Hydrocarbon Extraction and/or Separation Processes Utilizing a Membrane Separator

ABSTRACT

A membrane separator comprising a membrane is used to separate various streams in processes for separating aromatic hydrocarbons from non-aromatic hydrocarbons. Such streams can be a lean-solvent stream, a rich-solvent stream, or a hydrocarbon stream comprising both aromatic and non- aromatic hydrocarbons. The membrane separator is advantageously used in combination with an extraction sub-system including a liquid—liquid distillation column and/or an extraction distillation column.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of U.S. ProvisionalApplication No. 63/059,505 having a filing date of Jul. 31, 2020, thedisclosure of which is incorporated herein by reference in its entirety.

FIELD

This disclosure relates to processes, equipment, and systems forseparating and/or extracting aromatic hydrocarbons from a mixture feedcomprising aromatic and non-aromatic hydrocarbons. In particular, thisdisclosure relates to processes, equipment and systems for separating/orextracting aromatic hydrocarbons from a mixture feed comprising aromaticand non-aromatic hydrocarbons utilizing a membrane separator. Theprocesses, equipment, and systems of this disclosure are useful, e.g.,in producing aromatic hydrocarbon products such as benzene, toluene,xylenes, and non-aromatic hydrocarbon products from a mixture feedcomprising aromatic hydrocarbons and non-aromatic hydrocarbons.

BACKGROUND

Aromatic hydrocarbon products, such as benzene, toluene, xylenes,p-xylene, o-xylene, ethylbenzene, and the like, especially those withhigh purities, are highly valuable industrial commodities useful for theproduction of other value-added industrial chemicals. In a modernpetrochemical plant, aromatic hydrocarbon products are routinelyproduced by separating a mixture feed comprising one or more sucharomatic hydrocarbons and non-aromatic hydrocarbons. One example of suchmixture feed is a reformate stream, which can comprise non-aromatichydrocarbons at a high concentration, e.g., up to 30 wt %, based on thetotal weight of the reformate stream. Other examples of such mixturefeed include primarily aromatic hydrocarbon streams produced from axylenes isomerization unit, a transalkylation unit, or a toluenedisproportionation unit. Many of the non-aromatic hydrocarbons presentin the mixture feeds are co-boilers of the target aromatic hydrocarbons.As such, producing aromatic hydrocarbon products such as benzene,toluene, xylenes, p-xylene, o-xylene, and the like, from the mixturefeed, especially at a high purity, is difficult and inefficient, if notinfeasible, by using conventional distillation processes and equipment.

Solvent-assisted separation processes, such as liquid-liquid extractionprocesses and extraction distillation processes, have been used in theindustry for a long time to separate aromatic hydrocarbons from amixture feed. In such processes, typically a solvent with high polarity,such as sulfolane, tetraethylene glycol, and the like, is used tocontact the mixture feed in an extraction column. Because aromatichydrocarbon molecules typically exhibit a higher polarity thannon-aromatic hydrocarbons under the separation conditions, aromatichydrocarbons disproportionately distributes into the polar solvent toform an aromatic hydrocarbons-rich-solvent stream, which can besubsequently separated to produce high-purity aromatic hydrocarbons anda hydrocarbon-lean-solvent stream. The hydrocarbon-lean-solvent streamcan then be recycled to the extraction column. Thus, during theoperation of a continuous aromatic hydrocarbons extraction separationprocess, a quantity of polar solvent circulates in the system.

Overtime, the hydrocarbon-lean-solvent stream recycled to the extractioncolumn can experience a gradual increase of the concentrations ofvarious contaminants during an operation campaign. Such contaminants caninclude, among others, saturated and unsaturated heavy hydrocarbons,chlorine-containing compounds, silicon-containing compounds, and thelike, produced during the extraction process due to high temperatureconditions, and/or introduced through the mixture feed. Suchcontaminants, especially at a high concentration, can cause corrosionand/or fouling of the vessels, conduits, valves, pumps, and otherequipment, necessitating frequent shut-downs and maintenance, andseverely curtail the life of the system. Thus, an aromatic hydrocarbonsextraction system is frequently equipped with one or more solventregeneration units and/or stream purification units, such as steamstripping column, sorbent beds, and the like, to reduce contaminants inthe hydrocarbon-lean-solvent stream recycled to the extraction column.Alternatively, a portion of the hydrocarbon-lean-solvent stream may bepurged from time and time and replaced with fresh solvent feed. Allthese methods add to significant costs to the capital expenditure of theengineering and construction of a new aromatics plant, and the operationthereof.

Thus, there is a continued need for improvement for reducingcontaminants in the hydrocarbon-lean-solvent stream recycled to theextraction column in aromatic hydrocarbon extraction processes, and/orimprovement in the overall aromatic hydrocarbon production processes.This disclosure satisfies this and other needs.

SUMMARY

It has been found that in an aromatic hydrocarbon extraction process, amembrane separator can be used to separate a contaminant-containinglean-solvent stream (e.g., a recycle polar solvent stream comprisingappreciable quantity of heavy components as a portion of thecontaminants) to remove at least a portion of the contaminants in theretentate stream, thereby obtaining a purified lean-solvent stream,which can be preferably recycled to the extraction unit. Additionally, amembrane separator can be used to separate a hydrocarbon streamcomprising aromatic hydrocarbons and non-aromatic hydrocarbons to obtainan aromatic hydrocarbon-rich permeate stream and a non-aromatichydrocarbons-rich retentate stream. Further, a membrane separator can beused to separate a rich-solvent stream to obtain anon-aromatic-hydrocarbons-rich retentate stream and anaromatic-hydrocarbons-rich permeate stream, where the former can beadvantageously recycled to the extraction column, and aromatichydrocarbons can be recovered from the latter. The use of a membraneseparator in these processes can be a cost-effective, energy-efficientimprovement to existing processes for separating aromatic hydrocarbons.

Thus, a first aspect of this disclosure relates to a process forextracting aromatic hydrocarbons from a mixture feed comprising aromatichydrocarbons and non-aromatic hydrocarbons. The process can comprise(A-1) feeding the mixture feed into an extraction column. The processcan further comprise (A-2) providing a first lean-solvent streamcomprising a polar solvent at a concentration of c(ps) wt %, and heavycomponents at a total concentration of c(hcom) wt %, based on the totalweight of the lean-solvent stream, preferably 75≤c(ps) ≤99.99. Theprocess can further comprise (A-3) feeding the first lean-solvent streaminto a membrane separator, wherein: the membrane separator comprises avessel having a first volume, a second volume, and a membrane betweenthe first volume and the second volume; the first volume is separatedfrom the second volume by the membrane; the membrane is more permeableto the polar solvent than to the heavy components; and the firstlean-solvent stream is fed into the first volume. The process canfurther comprise (A-4) obtaining a retentate stream exiting the firstvolume of the membrane separator, wherein the retentate steam is rich inthe heavy components relative to the first lean-solvent stream. Theprocess can further comprise (A-5) obtaining a permeate stream exitingthe second volume of the membrane separator, wherein the permeate streamis depleted in the heavy components relative to the first lean-solventstream. The process can further comprise (A-6) feeding at least aportion of the permeate stream into the extraction column.

A second aspect of this disclosure relates to a process for separating amixture feed comprising aromatic hydrocarbons and non-aromatichydrocarbons. The process can comprise (B-1) feeding the mixture feedinto a membrane separator, wherein: the membrane separator comprises avessel having a first volume, a second volume, and a membrane betweenthe first volume and the second volume; the first volume is separatedfrom the second volume by the membrane; the membrane is more permeableto the aromatic hydrocarbons than to the non-aromatic hydrocarbons; andthe mixture feed is fed into the first volume. The process can furthercomprise (B-2) obtaining a retentate stream exiting the first volume ofthe membrane separator, wherein the retentate steam is depleted in thearomatic hydrocarbons and rich in the non-aromatic hydrocarbons relativeto the mixture feed. The process can further comprise (B-3) obtaining apermeate stream exiting the second volume of the membrane separator,wherein the permeate stream is rich in the aromatic hydrocarbons anddepleted in the non-aromatic hydrocarbons relative to the mixture feed.

A third aspect of this disclosure relates to a process for separating amixture feed comprising aromatic hydrocarbons and non-aromatichydrocarbons. The process can comprise (C-1) feeding the mixture feedand a first lean-solvent stream comprising a polar solvent into anextraction column. The process can further comprise (C-2) obtaining anoverhead stream and a bottoms stream from the extraction column, whereinthe overhead stream is rich in non-aromatic hydrocarbons relative to themixture feed, the bottoms stream is rich in aromatic hydrocarbons andthe polar solvent relative to the mixture feed. The process can furthercomprise (C-3) feeding at least a portion of the bottoms stream into amembrane separator, wherein: the membrane separator comprises a vesselhaving a first volume, a second volume, and a membrane between the firstvolume and the second volume; the first volume is separated from thesecond volume by the membrane; the membrane is more permeable to thearomatic hydrocarbons than to the non-aromatic hydrocarbons; and the atleast a portion of the bottoms stream is fed into the first volume. Theprocess can further comprise (C-4) obtaining a retentate stream exitingthe first volume of the membrane separator, wherein the retentate steamis depleted in the aromatic hydrocarbons and rich in the non-aromatichydrocarbons relative to the bottoms stream. The process can furthercomprise (C-5) obtaining a permeate stream exiting the second volume ofthe membrane separator, wherein the permeate stream is rich in thearomatic hydrocarbons and depleted in the non-aromatic hydrocarbonsrelative to the bottoms stream. The process can further comprise (C-6)feeding at least a portion of the retentate stream to the extractioncolumn.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the structure and operationof a membrane separator useful in embodiments of the processes of thisdisclosure.

FIG. 2 is a schematic diagram showing an exemplary extractionprocess/system for separating aromatic hydrocarbons from a mixture feedcomprising aromatic hydrocarbons and non-aromatic hydrocarbons includinga membrane separator to clean a stream of hydrocarbon-lean solvent,according to an embodiment of the first aspect of this disclosure.

FIGS. 3 and 4 are schematic diagrams showing exemplary extractionprocesses/systems for separating aromatic hydrocarbons from a mixturefeed comprising aromatic hydrocarbons and non-aromatic hydrocarbonsusing a membrane separator, according to an embodiment of the secondaspect of this disclosure.

FIG. 5 is a schematic diagram showing an exemplary extractionprocess/system for separating aromatic hydrocarbons from a mixture feedcomprising aromatic hydrocarbons and non-aromatic hydrocarbons using amembrane separator, according to an embodiment of the third aspect ofthis disclosure.

DETAILED DESCRIPTION

Definitions

In the present disclosure, a process is described as comprising at leastone “step.” It should be understood that each step is an action oroperation that may be carried out once or multiple times in the process,in a continuous or discontinuous fashion. Unless specified to thecontrary or the context clearly indicates otherwise, each step in aprocess may be conducted sequentially in the order as they are listed,with or without overlapping with one or more other step(s), or in anyother order, as the case may be. In addition, one or more or even allsteps may be conducted simultaneously with regard to the same ordifferent batch of material. For example, in a continuous process, whilea first step in a process is being conducted with respect to a rawmaterial just fed into the beginning of the process, a second step maybe carried out simultaneously with respect to an intermediate materialresulting from treating the raw materials fed into the process at anearlier time in the first step. Preferably, the steps are conducted inthe order described.

Unless otherwise indicated, all numbers indicating quantities in thepresent disclosure are to be understood as being modified by the term“about” in all instances. It should also be understood that the precisenumerical values used in the specification and claims constitutespecific embodiments. Efforts have been made to ensure the accuracy ofthe data in the examples. However, it should be understood that anymeasured data inherently contain a certain level of error due to thelimitation of the technique and equipment used for making themeasurement.

As used herein, the indefinite article “a” or “an” shall mean “at leastone” unless specified to the contrary or the context clearly indicatesotherwise. Thus, embodiments using “a distillation column” includeembodiments where one, two or more distillation columns are used, unlessspecified to the contrary or the context clearly indicates that only onedistillation column is used. Likewise, “a C9+ stream” should beinterpreted to include one, two, or more C9+ components, unlessspecified or indicated by the context to mean only one specific C9+component.

As used herein, “wt %” means percentage by weight, “vol %” meanspercentage by volume, “mol %” means percentage by mole, “ppm” meansparts per million, and “ppm wt” and “wppm” are used interchangeably tomean parts per million on a weight basis. All “ppm”, as used herein, areppm by weight unless specified otherwise. All concentrations herein areexpressed on the basis of the total amount of the composition inquestion. Thus, e.g., the concentrations of the various components of afeed composition are expressed based on the total weight of the feedcomposition. All ranges expressed herein should include both end pointsas two specific embodiments unless specified or indicated to thecontrary.

“Hydrocarbon” means (i) any compound consisting of hydrogen and carbonatoms or (ii) any mixture of two or more such compounds in (i). The term“Cn hydrocarbon,” where n is a positive integer, means (i) anyhydrocarbon compound comprising carbon atom(s) in its molecule at thetotal number of n, or (ii) any mixture of two or more such hydrocarboncompounds in (i). The term “Cn aromatic hydrocarbon,” where n is apositive integer, means (i) any aromatic hydrocarbon compound comprisingcarbon atom(s) in its molecule at the total number of n, or (ii) anymixture of two or more such aromatic hydrocarbon compounds in (i). Thus,a C2 hydrocarbon can be ethane, ethylene, acetylene, or mixtures of atleast two of them at any proportion. A “Cm to Cn hydrocarbon” or “Cm-Cnhydrocarbon,” where m and n are positive integers and m<n, means any ofCm, Cm+1, Cm+2, Cn−1, Cn hydrocarbons, or any mixtures of two or morethereof. Thus, a “C2 to C3 hydrocarbon” or “C2-C3 hydrocarbon” can beany of ethane, ethylene, acetylene, propane, propene, propyne,propadiene, cyclopropane, and any mixtures of two or more thereof at anyproportion between and among the components. A “saturated C2-C3hydrocarbon” can be ethane, propane, cyclopropane, or any mixturethereof of two or more thereof at any proportion. A “Cm to Cn aromatichydrocarbon” or “Cm-Cn hydrocarbon,” where m and n are positive integersand m<n, means any of Cm, Cm+1, Cm+2, Cn−1, Cn aromatic hydrocarbons, orany mixtures of two or more thereof. A “Cn+hydrocarbon” means (i) anyhydrocarbon compound comprising carbon atom(s) in its molecule at thetotal number of at least n, or (ii) any mixture of two or more suchhydrocarbon compounds in (i). A “Cn-hydrocarbon” means (i) anyhydrocarbon compound comprising carbon atoms in its molecule at thetotal number of at most n, or (ii) any mixture of two or more suchhydrocarbon compounds in (i). A “Cm hydrocarbon stream” means ahydrocarbon stream consisting essentially of Cm hydrocarbon(s). A “Cm-Cnhydrocarbon stream” means a hydrocarbon stream consisting essentially ofCm-Cn hydrocarbon(s). A “Cn+aromatic hydrocarbon” means (i) any aromatichydrocarbon compound comprising carbon atom(s) in its molecule at thetotal number of at least n, or (ii) any mixture of two or more sucharomatic hydrocarbon compounds in (i). A “Cn−aromatic hydrocarbon” means(i) any aromatic hydrocarbon compound comprising carbon atoms in itsmolecule at the total number of at most n, or (ii) any mixture of two ormore such aromatic hydrocarbon compounds in (i). A “Cm aromatichydrocarbon stream” means a hydrocarbon stream consisting essentially ofCm aromatic hydrocarbon(s). A “Cm-Cn aromatic hydrocarbon stream” meansa hydrocarbon stream consisting essentially of Cm-Cn aromatichydrocarbon(s).

An “aromatic hydrocarbon” is a hydrocarbon comprising an aromatic ringin the molecule structure thereof. A “non-aromatic hydrocarbon” means ahydrocarbon other than an aromatic hydrocarbon.

“Co-boiler” means a compound having a normal boiling point in proximityto that of a reference compound or product. For example, where areference compound or product has a normal boiling point of bp ° C., aco-boiler thereof can have a normal boiling point in the range of bp±30°C., bp±25° C., bp±20° C., bp±15° C., bp±10° C., or bp±5° C. A co-boilerof a reference compound can have a relative volatility in a range from,e.g., 0.5 to 5, or 0.5 to 3, or 0.5 to 2, or 0.5 to 1.5. Typicalco-boilers of benzene include, but not are not limited to:methylcyclopentane, cyclohexane, 2,3-dimethylpentane,dimethylcyclopentanes, ethylcyclopentane, and 3-methylhexane. Due toclose boiling points, conventional distillation typically cannot beeconomically used to separate co-boilers from a reference compound orproduct. Major non-aromatic co-boilers of aromatic hydrocarbons presentin petrochemical products and petrochemical process streams tend tocomprise linear, branched, and/or cyclic alkanes and olefins at totalhigh concentration thereof of, e.g., 60 wt %, 70 wt %, 80 wt %, 90 wt %,95 wt %, or even 98 wt %, based on the total weight of the non-aromaticco-boilers.

“Heavy components” as used herein means components that may be presentin a lean-solvent stream differing from the solvent and having a normalboiling point of at least 140° C., e.g., 150° C., 160° C., 180° C., andeven 200° C.

“Xylene,” either in singular or plural form, shall collectively mean oneof or any mixture of two or three of para-xylene, meta-xylene, andortho-xylene at any proportion thereof.

“Rich” or “enriched” when describing a component in a stream means thatthe stream comprises the component at a concentration higher than asource material from which the stream is derived. “Depleted” whendescribing a component in a stream means that the stream comprises thecomponent at a concentration lower than a source material from which thestream is derived. Thus, in embodiments where an admixture streamcomprising an aromatic hydrocarbon and a non-aromatic hydrocarbon isseparated by a membrane separator comprising a membrane to produce apermeate stream comprising the aromatic hydrocarbon at a higherconcentration than the admixture stream and the non-aromatic hydrocarbonat a lower concentration than the admixture stream, the permeate streamis rich or enriched in the aromatic hydrocarbon and depleted in thenon-aromatic hydrocarbon relative to the admixture stream.

“Lean” means depleted. A “lean-solvent,” or “lean solvent,” or“hydrocarbon-lean solvent” in this disclosure interchangeably means acomposition or stream depleted in hydrocarbon(s) and consistingessentially of solvent. A “rich-solvent,” “rich solvent,” or“hydrocarbon-rich solvent” in this disclosure interchangeably means acomposition or stream comprising solvent and rich in hydrocarbon(s).

“Consisting essentially of” as used herein means the composition, feed,or effluent comprises a given component at a concentration of at least60 wt %, preferably at least 70 wt %, more preferably at least 80 wt %,more preferably at least 90 wt %, still more preferably at least 95 wt%, based on the total weight of the composition, feed, or effluent inquestion.

Nomenclature of elements and groups thereof used herein are pursuant tothe Periodic Table used by the International Union of Pure and AppliedChemistry after 1988. An example of the Periodic Table is shown in theinner page of the front cover of Advanced Inorganic Chemistry, 6thEdition, by F. Albert Cotton et al. (John Wiley & Sons, Inc., 1999).

Membrane Separator

A membrane separator useful in the processes according to the variousaspects of this disclosure can comprise a vessel having a first volume,a second volume, and a membrane between the first volume and the secondvolume. The first volume is separate from the second volume by themembrane. An admixture stream comprising a first component and a secondcomponent having a lower polarity than the first component is suppliedinto the first volume. The membrane is selected to have a polarity suchthat it is more permeable to the first component than to the secondcomponent. Thus, on contacting the admixture stream, the membranepreferentially permits the first component to permeate through to enterinto the second volume, from which a permeate stream rich in the firstcomponent and depleted in the second component relative to the admixturestream exits. A retentate stream exiting the first volume becomesdepleted in the first component and rich in the second componentrelative to the admixture stream. The permeation of component(s) throughthe membrane is preferentially facilitated by a pressure drop from thefirst volume to the second volume. Structure and operation of exemplarymembrane separator are provided in FIG. 1 and described in greaterdetail below.

The membrane can be polymer-based. The term polymer includes, but is notlimited to, homopolymers, copolymers, terpolymers, polymer blends, andthe like. For example, suitable polymers for the membrane include, butare not limited to, polyesters, polyethers, polysulfones, polyimides,polyamides, polymers derived from bisphenol-A dianhydride, polyvinylalcohols, polyacrylonitriles, polyurethanes, polyureas, polyacrylicacids, polyacrylates, elastomeric polymers such as polybutadiene,polyisoprenes, polyvinylpyridines, halogenated polymers,fluoroelastomers, polyvinyl halides, polysiloxanes, poly dimethylsiloxanes, a copolymer comprising at least one of the foregoingpolymers, a blend comprising at least one of the foregoing polymers, analloy comprising at least one of the foregoing polymers, or acombination comprising at least one of the foregoing polymers,copolymers, blends, or alloys. The polymers could be further physicallyor chemically ross-linked to increase chemical stability.

In various preferred embodiments, the membrane can be a polyimide-basedmembrane treated by a lubricating oil. In other embodiments, themembrane can comprise an ionic liquid carried by an organic or inorganicmatrix material.

In various preferred embodiments, during operation, the admixture streamsupplied into the first volume is in liquid phase. Preferably, duringoperation, a positive pressure gradient of deltaP kPa exists between thefirst volume and the second volume, facilitating the permeation of thefirst component from the first volume into the second volume.Preferably, deltaP can ranges from deltaP1 to deltaP2, where deltaP1 anddeltaP2 can be, independently, e.g., 345, 350, 400, 450, 500, 600, 700,800, 900, 1,000, 1,500, 2,000, 2,500, 3,000, 3,447, 3,500, 4,000, 4,500,5,000, 5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500,10,000, 10,342, as long as deltaP1 <deltaP2. Preferably deltaP1=3,447and deltaP2=8,274.

Description of exemplary membranes, membrane separators, and membraneseparation processes useful in the processes of the aspects of thisdisclosure include, e.g., U.S. Pat. Nos. 4,571,444; 6,187,987;6,180,008; and 7,642,393; and Zhang, Fan, “Selective Separation ofToluene/n-Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4],”Chem. Eng. Technol. 2015, 38, No. 2, 355-361, the relevant contents inwhich are incorporated herein by reference.

Liquid-Liquid Extraction Processes for Separating a Mixture FeedComprising Aromatic Hydrocarbons and Non-Aromatic Hydrocarbons

Liquid-liquid extraction (“LLE”) processes have been used to separatearomatic hydrocarbons from a mixture comprising aromatic andnon-aromatic hydrocarbons. An LLE unit can include a LLE columnreceiving a feed mixture stream at one location on the column and apolar solvent stream at another location above the feed mixture stream.The solvent stream typically flows downwards to mix with the feedmixture. The polar solvent, e.g., sulfolane, preferentially extracts thearomatic hydrocarbons, due to their higher polarity than thenon-aromatic hydrocarbons, to form a rich-solvent stream rich inaromatic hydrocarbons relative to the feed mixture stream exiting thebottom of the column. Non-aromatic hydrocarbons then preferentially flowupwards and exit as an overhead stream. An LLE column is operated atrelatively low temperature such that substantially all materials in thecolumn are in liquid phase. An overall LLE unit can also includeadditional equipment such as one or more stripping column for processingthe overhead stream and the rich-solvent stream, and at least onerecovery column for recovering high-purity aromatic hydrocarbons from amixture of the polar solvent and the aromatic hydrocarbons, which alsoproduces a lean-solvent stream. The lean solvent may be partlyregenerated and/or cleaned, and then recycled to the LLE column.

Description of exemplary liquid-liquid extraction equipment and processcan be found in, e.g., U.S. Pat. Nos. 4,039,389 and 6,569,390, therelevant contents of both of which are incorporated herein by reference.

Extraction Distillation Processes for Separating a Mixture FeedComprising Aromatic Hydrocarbons and Non-Aromatic Hydrocarbons

Extractive distillation (“ED”) processes have been used to separatearomatic hydrocarbons from a mixture comprising aromatic andnon-aromatic hydrocarbons as well. An ED unit can include an ED columnreceiving a feed mixture stream at one location on the column and apolar solvent stream at another location above the feed mixture stream.The solvent stream typically flows downwards to mix with the feedmixture. The polar solvent, e.g., sulfolane, preferentially extracts thearomatic hydrocarbons, due to their higher polarity than thenon-aromatic hydrocarbons, to form a rich-solvent stream in liquid phaseand rich in aromatic hydrocarbons relative to the feed mixture streamexiting the bottom of the column. Non-aromatic hydrocarbons thenpreferentially flow upwards and exit as an overhead stream in vaporphase. In comparison to an LLE column, an ED column is operated athigher temperature such that the overhead effluent is substantially invapor phase. An overall ED unit can also include additional equipmentsuch as one or more stripping column for processing the overhead streamand the rich-solvent stream, and at least one recovery column forrecovering high-purity aromatic hydrocarbons from a mixture of the polarsolvent and the aromatic hydrocarbons, which also produces alean-solvent stream. The lean solvent may be partly regenerated and/orcleaned, and then recycled to the ED column.

Description of exemplary extraction distillation equipment and processcan be found in, e.g., WO2012/135111; U.S. Patent ApplicationPublication No. 20100270213; U.S. Pat. Nos. 3723256; 4,234,544;4,207,174; and 5,310,480; the relevant contents of all of which areincorporated herein by reference.

Processes of the First Aspect of This Disclosure

A first aspect of this disclosure relates to process for extractingaromatic hydrocarbons from a mixture feed comprising aromatichydrocarbons and non-aromatic hydrocarbons, the process comprising:

(A-1) feeding the mixture feed into an extraction column;

(A-2) providing a first lean-solvent stream comprising a polar solventat a concentration of c(ps) wt %, and heavy components at a totalconcentration of c(hcom) wt %, based on the total weight of thelean-solvent stream, where 75 ≤c(ps) ≤99.99;

(A-3) feeding the first lean-solvent stream into a membrane separator,wherein: the membrane separator comprises a vessel having a firstvolume, a second volume, and a membrane between the first volume and thesecond volume; the first volume is separated from the second volume bythe membrane; the membrane is more permeable to the polar solvent thanto the heavy components; and the first lean-solvent stream is fed intothe first volume;

(A-4) obtaining a retentate stream exiting the first volume of themembrane separator, wherein the retentate steam is rich in the heavycomponents relative to the first lean-solvent stream;

(A-5) obtaining a permeate stream exiting the second volume of themembrane separator, wherein the permeate stream is depleted in the heavycomponents relative to the first lean-solvent stream; and

(A-6) feeding at least a portion of the permeate stream into theextraction column.

In certain embodiments of the process of the first aspect, the processmay further comprise (A-7) phase separating at least a portion of theretentate stream to obtain a heavy components stream and a solventstream saturated with heavy components; and (A-8) feeding at least aportion of the solvent stream saturated with heavy components to theextraction column. In such embodiments, the solvent stream saturatedwith heavy components may comprise the heavy components at a totalconcentration in a range from 3 to 15 wt %, based on the total weight ofthe solvent stream saturated with the heavy components, e.g., 3 wt %, 4wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %,13 wt %, 14 wt %, or 15 wt %. The step of phase separating in (A7) canbe conveniently carried out in a column receiving the retentate streamat a location between the top and the bottom, and discharging the heavycomponents stream in the vicinity of the top and the solvent streamsaturated with heavy components in the vicinity of the bottom, where thesolvent has a higher density than the heavy components. Preferably noadditional heat is input into the phase-separating column to effect thephase separation. The heavy components stream can be conducted away as aby-product, or alternatively or additionally separated and processed toproduce other products.

The extraction column used in step (A-1) can be a liquid-liquidextraction column or an extraction distillation column described above,or a combination of both. Preferably, the extraction column is anextraction distillation column.

The polar solvent useful in the processes of this disclosure can be anysuch solvent known in the art. Non-limiting examples of such polarsolvent are: tetraethylene glycol, triethylene glycol, diethyleneglycol, ethylene glycol, methoxy triglycol ether, diglycolamine,dipropylene glycol, N-formyl morpholine, N-methyl pyrrolidone,2,3,4,5-tetrahydrothiophene-1, 1-dioxide (“sulfolane”),3-methylsulfolane and dimethyl sulfoxide, tetramethylenesulfone,mixtures thereof, and/or admixtures with water thereof. A particularlypreferred polar solvent is sulfolane.

To facilitate effective and efficient separation in the membraneseparator, the first lean-solvent stream can have a temperature T in arange from, e.g., 25 to 80° C. (e.g., 25° C., 26° C., 28° C., 30° C.,35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 70° C., 72° C., 74° C.,75° C., 76° C., 78° C., or 80° C.) when fed into the membrane separator,and a positive pressure gradient of deltaP kPa exists from the firstvolume to the second volume of the membrane separator, and deltaP canranges from deltaP1 to deltaP2 kilopascal, where deltaP1 and deltaP2 canbe, independently, e.g., 345, 350, 400, 450, 500, 600, 700, 800, 900,1,000, 1,500, 2,000, 2,500, 3,000, 3,447, 3,500, 4,000, 4,500, 5,000,5,500, 6,000, 6,500, 7,000, 7,500, 8,000, 8,500, 9,000, 9,500, 10,000,10,342, as long as deltaP1 <deltaP2. Preferably deltaP1=3,447 anddeltaP2=8,274.

The first lean-solvent stream can comprise the polar solvent at aconcentration of c(ps) wt %, and the heavy components at a totalconcentration of c(hcom) wt %, based on the total weight of thelean-solvent stream, where c(ps) can range from c(ps)1 to c(ps)2, c(ps)1and c(ps)2 can be, independently, e.g., 75, 76, 77, 78, 79, 80, 82, 84,85, 86, 88, 90, 92, 94, 95, 96, 97, 98, 99, 99.9, and 99.99, as long asc(ps)1 <c(ps)2; and c(hcom) can range from c(hcom)1 to c(hcom)2, andc(hcom)1 and c(hcom)2 can be, independently, e.g., 0.01, 0.02, 0.03,0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7,0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,29, 20, as long as c(hcom)1 <c(hcom)2. Preferably c(ps)1 85 and c(hcom)2≤15. Preferably c(ps)1 ≥90 and c(hcom)2 ≤10. Preferably c(ps)1 ≥92 andc(hcom)2 ≤8.

In certain embodiments of the process of the first aspect, the processfurther comprises (A-9) feeding a second lean-solvent stream comprisingthe polar solvent into the extraction column. In certain specificembodiments, in a given time period, the first lean-solvent streamcomprises the polar solvent at a total weight of W1, the secondlean-solvent stream comprises the polar solvent at a total weight of W2,and 0.5% W1/(W1+W2)*100% 10%. The value of W1/(W1+W2)*100% may rangefrom v1% to v2%, where v1 and v2 can be, independently, e.g., 0.5, 0.6,0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Preferably r1=1 and r2=5.Preferably r1=1 and r2=3. In these embodiments, compared to the quantityof the polar solvent supplied directly into the extraction column, W2,the quantity of the polar solvent in the first lean-solvent stream,subjected to membrane separation and purification, W1, is relativelysmall. In certain specific embodiments, the first lean-solvent streamand the second lean-solvent stream are derived from a commonlean-solvent stream, e.g., as two split streams from the commonlean-solvent stream. The common lean-solvent stream can be a recyclesolvent stream produced from, e.g., a distillation column separating arich-solvent stream consisting essentially of the polar solvent andaromatic hydrocarbons. Although only a small fraction of the recyclelean-solvent stream is subjected to heavy components abatement using themembrane separator, the cumulative amount of heavy components removedand abated by the membrane separator can be significant over a prolongedoperation campaign, capable of significantly increase the service lifeof the batch of the polar solvent circulating in the extraction system,with or without using additional means to further purify the polarsolvent in circulation such as sorbent beds, vacuum regeneration column,and steam stripping solvent regenerator. In certain specificembodiments, where the common lean-solvent stream comprise the heavycomponents at a total concentration of c(hcom-cs) wt %, based on thetotal weight of the common lean-solvent stream, and the process furthercomprises: (A-10) monitoring c(hcom-cs); and (A-11) implementing steps(A-3) to (A-8) only if c(hcom-cs)≥1, e.g., if c(hcom-cs) ≥2, ifc(hcom-cs)≥3, if c(hcom-cs) ≥4, if c(hcom-cs) ≥5, if c(hcom-cs) ≥6, ifc(hcom-cs) ≥7, if c(hcom-cs) ≥8, if c(hcom-cs) ≥9, if c(hcom-cs) ≥10, ifc(hcom-cs) ≥11. In these embodiments, the steps (A-3)-(A-8) are onlyimplemented when the common lean-solvent stream comprises the heavycomponents at an appreciable concentration, e.g., only after the polarsolvent has been circulated in the extraction separation system for aprolonged period of time.

In various embodiments of the process of the first aspect, the processmay further comprise: (A-12) obtaining a bottoms stream from theextraction column, wherein the bottoms stream is rich in aromatichydrocarbons and the polar solvent relative to the mixture feed; (A-13)separating at least a portion of the bottoms stream in a strippingcolumn to obtain an aromatic hydrocarbons-rich stream depleted in thepolar solvent relative to the bottoms stream, and a third lean-solventstream depleted in aromatic hydrocarbons relative to the bottoms stream;and (A-14) deriving at least one of the first lean-solvent stream, thesecond lean-solvent stream, and the common lean-solvent stream from thethird lean-solvent stream. In these embodiments, a circulation loop ofthe polar solvent exists in the overall process. As discussed above,steps (A3)-(A8), where implemented, function to purity at least aportion of the recycle lean-solvent stream to prolong the service lifethereof in the overall process and system. In step (A-13), an optionalsteam stream may be fed into the stripping column. In step (A-13), asteam-rich overhead stream may be obtained from the stripping column,which can be condensed and separated to obtain a water stream and an oilstream.

In certain specific embodiments comprising steps (A-12) to (A-14), theprocess may further comprise (A-15) deriving a fourth lean-solventstream from the third lean-solvent stream; (A-16) regenerating thefourth lean-solvent stream in a steam stripping regeneration columnand/or a vacuum regeneration column to obtain a regenerated lean-solventstream comprising steam and a bottoms heavy stream; and (A-17) feedingthe regenerated lean-solvent stream into one or more of: the strippingcolumn, the extraction column, and the membrane separator as at least aportion of the first lean-solvent stream. In these embodiments, aregeneration column is utilized to further purify a lean-solvent stream,further prolonging the service life of the polar solvent in the process.In specific embodiments, the process further comprises (A-18) condensingat least a portion of the aromatic hydrocarbons-rich stream to obtain amixture comprising an aqueous liquid phase and an oil liquid phase;(A-19) separating the aqueous liquid phase to obtain a water stream;(A-20) heating the water stream to obtain a steam stream; and (A-21)feeding the steam stream to the steam stripping regeneration column. Incertain specific embodiments, in step (A-21), the steam stream is atleast partly heated by a portion of the third lean-solvent stream.

Compared to using only sorbent beds to purify a polar solvent stream asis known in the art, which consumes the sorbent necessitating periodicsorbent bed change-out, the process of this disclosure using a membraneseparator has the advantage of producing much less waste and incurringmuch lower costs. Compared to using only a steam stripping solventregenerator or a vacuum regenerator to purify a polar solvent stream asis known in the art, the process of this disclosure using a membraneseparator has the advantage of much less energy consumption, producingless waste water, improved abatement of the heavy components from thelean-solvent stream(s) because the capability of a steam regenerationcolumn is limited by the temperature of the steam or the temperature ofthe vacuum column, and lower rate of degradation of the polar solventbecause the membrane separator operates at a much lower temperature thana steam regeneration column or a vacuum regenerator. In addition, theprocess of this disclosure using a membrane separator has the advantageof ability to separate and abate heavy components co-boiling with thepolar solvent or heavier than the polar solvent from the polar solvent,which a process using steam stripping regeneration or vacuumregeneration cannot separate or reduce from the polar solvent.

Processes of the Second Aspect of This Disclosure

A second aspect of this disclosure relates to a process for separating amixture feed comprising aromatic hydrocarbons and non-aromatichydrocarbons, the process comprising:

(B-1) feeding the mixture feed into a membrane separator, wherein: themembrane separator comprises a vessel having a first volume, a secondvolume, and a membrane between the first volume and the second volume;the first volume is separated from the second volume by the membrane;the membrane is more permeable to the aromatic hydrocarbons than to thenon-aromatic hydrocarbons; and the mixture feed is fed into the firstvolume;

(B-2) obtaining a retentate stream exiting the first volume of themembrane separator, wherein the retentate steam is depleted in thearomatic hydrocarbons and rich in the non-aromatic hydrocarbons relativeto the mixture feed; and

(B-3) obtaining a permeate stream exiting the second volume of themembrane separator, wherein the permeate stream is rich in the aromatichydrocarbons and depleted in the non-aromatic hydrocarbons relative tothe mixture feed.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-4) feeding at least a portion of the retentatestream and an extraction solvent stream into an extraction sub-system;(B-5) obtaining from the extraction sub-system a non-aromatichydrocarbons stream, an extracted aromatic hydrocarbons stream, and alean-solvent stream; and (B-6) recycling at least a portion of thelean-solvent stream into the extraction sub-system as at least a portionof the extraction solvent stream.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-7) feeding at least a portion of the permeatestream and at least a portion of the extracted aromatic hydrocarbonstream into an aromatic hydrocarbons distillation column; and (B-8)obtaining from the aromatic hydrocarbons distillation column two or morearomatic product streams.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-9) feeding at least a portion of the permeatestream and/or a least a portion of the extracted aromatic hydrocarbonstream into a reactor; and (B-10) producing a converted product mixturefrom the reactor.

In certain embodiments of the process of the second aspect, the mixturefeed comprises benzene, toluene, C8 aromatic hydrocarbons, non-aromatichydrocarbon co-boilers of benzene, non-aromatic hydrocarbon co-boilersof toluene, and non-aromatic hydrocarbon co-boilers of C8 aromatichydrocarbons, at a total concentration thereof ≥60 wt % (e.g., ≥65, ≥70,≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weight ofthe mixture feed.

In certain embodiments of the process of the second aspect, the mixturefeed comprises benzene, toluene, non-aromatic hydrocarbon co-boilers ofbenzene, and non-aromatic hydrocarbon co-boilers of toluene, at a totalconcentration thereof ≥60 wt % (e.g., ≥65, ≥70, ≥75, ≥80, ≥85, ≥90, ≥95,≥98, ≥99, wt %), based on the total weight of the mixture feed. SuchC6-C7 hydrocarbon mixture feed can be advantageously derived from, e.g.,distillation of a C6+ hydrocarbon stream derived from a hydrocarbonreformer comprising, in addition to C6-C7 hydrocarbons, C8, C9, andoptionally C9+ hydrocarbons.

In certain embodiments of the process of the second aspect, the mixturefeed comprises benzene and non-aromatic hydrocarbon co-boilers ofbenzene at a total concentration thereof ≥60 wt % (e.g., ≥65, ≥70, ≥75,≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weight of themixture feed.

In certain embodiments of the process of the second aspect, the mixturefeed comprises benzene at a concentration thereof ≥60 wt % (e.g., ≥65,≥70, ≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weightof the mixture feed.

In certain embodiments of the process of the second aspect, the mixturefeed comprises toluene and non-aromatic hydrocarbon co-boilers oftoluene at a total concentration thereof ≥60 wt % (e.g., ≥65, ≥70, ≥75,≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weight of themixture feed.

In certain embodiments of the process of the second aspect, the mixturefeed comprises toluene at a concentration thereof ≥60 wt % (e.g., ≥65,≥70, ≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weightof the mixture feed.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-11) providing an isomerization feed streamconsisting essentially of C8 aromatic hydrocarbons; (B-12) contactingthe isomerization feed stream with an isomerization catalyst in anisomerization zone under isomerization condition to produce anisomerization product mixture; (B-13) separating the isomerizationproduct mixture to obtain a C7−hydrocarbons-rich stream, and a C8+hydrocarbon-rich stream; and (B-14) providing at least a portion of theC7− hydrocarbons-rich stream as the at least a portion of the mixturefeed. B6a. In certain specific embodiments, the C7− hydrocarbons-richstream is substantially free of C8 hydrocarbons. In other specificembodiments, the C7− hydrocarbon-rich stream comprises C8 hydrocarbonsat a concentration from c(C8)1 to c(C8)2 wt %, based on the total weightof the C7− hydrocarbon-rich stream, where c(C8)1 and c(C8)2 can be,independently, e.g., 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20. Preferably c(C8)2 ≤10. Preferably c(C8)2 ≤5.

The isomerization conditions can include a temperature and a pressuresuch that a majority of the C8 aromatic hydrocarbons in theisomerization zone are in vapor phase (“vapor-phase isomerization” or“VPI”). Alternatively, the isomerization conditions can include atemperature and a pressure such that a majority of the C8 aromatichydrocarbons in the isomerization zone are in liquid phase(“liquid-phase isomerization” or “LPI”). LPI requires a lowertemperature than VPI, and can be carried out without co-feeding amolecular hydrogen stream into the isomerization zone. As such LPI maybe preferred in certain embodiments over VPI, especially where theisomerization feed stream comprises ethylbenzene at a low concentration.The VPI may be favored where the isomerization feed comprisesethylbenzene at a high concentration, e.g., ≥10 wt %, based on the totalweight of the isomerization feed stream, because VPI can be moreeffective than LPI in converting ethylbenzene. Description of exemplaryVPI processes and catalysts can be found in, e.g., U.S. PatentApplication Publication Nos. US20110319688A1; US20120108867A1;US20120108868A1; US20140023563A1; US20150051430A1; and US20170081259A1;the relevant contents of all of which are incorporated herein byreference. Description of exemplary LPI processes and catalysts can befound in, e.g., U.S. Patent Application Publication Nos.US20110319688A1; US20120108867A1; US20130274532A1; US20140023563A1; andUS20150051430A1; the relevant contents of all of which are incorporatedherein by reference.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-15) providing a transalkylation feed mixturecomprising C7−aromatic hydrocarbons and C9+ aromatic hydrocarbons;(B-16) contacting the transalkylation feed mixture with atransalkylation catalyst in a transalkylation zone under transalkylationconditions to produce a transalkylation effluent; (B-17) separating thetransalkylation effluent to obtain a benzene-rich stream, and a C8hydrocarbons-rich stream; and (B-18) providing at least a portion of thebenzene-rich stream as the at least a portion of the mixture feed.Description of exemplary transalkylation zone, transalkylation catalyst,and transalkylation conditions can be found in, e.g., U.S. Pat. Nos.7,663,010 and 8,183,424, the relevant contents of both of which areincorporated herein by reference.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-19) providing a toluene disproportionation feedconsisting essentially of toluene; (B-20) contacting the toluenedisproportionation feed with a toluene disproportionation catalyst in adisproportionation zone under disproportionation conditions to produce adisproportionation effluent; (B-21) separating the disproportionationeffluent to obtain a benzene-rich stream, and a C8 hydrocarbons-richstream; and (B-22) providing at least a portion of the benzene-richstream as the at-least a portion of the mixture feed. Description ofexemplary disproportionation zone, disproportionation catalysts, anddisproportionation conditions can be found in, e.g., U.S. Pat. Nos.6,486,373; 7,326,818; and 10,661,258; the relevant contents of all ofwhich are incorporated herein by reference. The disproportionationcatalyst can be shape-selective or non-shape-selective. If ashape-selective catalyst is used, the disproportionation effluent maycomprise p-xylene at a concentration significantly higher than m-xyleneand/or o-xylene, and ethylbenzene at a low concentration, based on thetotal weight of all C8 aromatic hydrocarbons in the disproportionationeffluent, which can be highly advantageous for the purpose ofco-production of a p-xylene product from the process of the first aspectof this disclosure.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-23) providing a C6+ hydrocarbons stream comprisingbenzene, non-aromatic benzene co-boilers, toluene, non-aromatic tolueneco-boilers, C8 aromatic hydrocarbons, non-aromatic co-boilers of C8aromatic hydrocarbons, and C9+ hydrocarbons; (B-24) separating the C6+hydrocarbons stream to obtain a C7− hydrocarbons stream rich in benzeneand toluene, a C7-C8 hydrocarbons stream rich in C8 hydrocarbons, and aC9+ hydrocarbons stream rich in C9+ hydrocarbons; and (B-25) feeding atleast a portion of the C7− hydrocarbon stream into the membraneseparator as at least a portion of the mixture feed. Such C6+hydrocarbons stream can be derived from, e.g., an effluent from ahydrocarbons reformer in a petrochemical plant. In specific embodiments,the process may further comprise (B-26) feeding at least a portion ofthe C7− hydrocarbon stream into the extraction sub-system column.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-23) conducting away at least a portion of theretentate stream and/or at least a portion of the non-aromatichydrocarbon stream. In certain specific embodiments, in step (B-23), theat least a portion of the retentate stream and/or the at least a portionof the non-aromatic hydrocarbon stream is used as a mogas blendingstock.

In certain embodiments of the process of the second aspect, the processfurther comprises (B-24) feeding at least a portion of the retentatestream into the extraction sub-system.

Processes of the Third Aspect of This Disclosure

A third aspect of this disclosure relates to a process for separating amixture feed comprising aromatic hydrocarbons and non-aromatichydrocarbons, the process comprising:

(C-1) feeding the mixture feed and a first lean-solvent streamcomprising a polar solvent into an extraction column;

(C-2) obtaining an overhead stream and a bottoms stream from theextraction column, wherein the overhead stream is rich in non-aromatichydrocarbons relative to the mixture feed, the bottoms stream is rich inaromatic hydrocarbons and the polar solvent relative to the mixturefeed;

(C-3) feeding at least a portion of the bottoms stream into a membraneseparator, wherein: the membrane separator comprises a vessel having afirst volume, a second volume, and a membrane between the first volumeand the second volume; the first volume is separated from the secondvolume by the membrane; the membrane is more permeable to the aromatichydrocarbons than to the non-aromatic hydrocarbons; and the at least aportion of the bottoms stream is fed into the first volume;

(C-4) obtaining a retentate stream exiting the first volume of themembrane separator, wherein the retentate steam is depleted in thearomatic hydrocarbons and rich in the non-aromatic hydrocarbons relativeto the bottoms stream;

(C-5) obtaining a permeate stream exiting the second volume of themembrane separator, wherein the permeate stream is rich in the aromatichydrocarbons and depleted in the non-aromatic hydrocarbons relative tothe bottoms stream; and

(C-6) feeding at least a portion of the retentate stream to theextraction column

The extraction column may be a liquid-liquid extraction column, anextraction distillation column, a combination of both types.

In various embodiments of the processes of the third aspect, the processmay comprise (C-7) obtaining at least an aromatic hydrocarbons-richstream and a second lean-solvent stream from the permeate stream,wherein the second lean-solvent stream is rich in the polar solventrelative to the permeate steam; and (C-8) recycling at least a portionof the second lean-solvent stream to the extraction column as at least aportion of the first lean-solvent stream. Step (C-7) can be carried outin a single or multiple columns optionally including a stripping column.Where the extraction column is an extraction distillation column,preferably a single distillation column is used in step (C-7), which maybe called a “recovery column.” Where the extraction column is aliquid-liquid extraction column, step (C-7) can be carried out first byfeeding at least a portion of the permeate stream to a striping column,from which a stream rich in non-aromatic hydrocarbons and a bottomsstream rich in aromatic hydrocarbons and the polar solvent are produced.An optional steam stream may be fed into the stripping column. Asteam-rich overhead stream may be obtained from the stripping column,which can be condensed and separated to obtain a water stream and an oilstream. The bottoms stream from the stripping column can be then fedinto a recovery column from which the aromatic hydrocarbons-rich streamis obtained from the top and the second lean-solvent stream is obtainedfrom the bottom. Additionally or alternatively, where in the extractioncolumn is a liquid-liquid extraction column, at least a portion of thepermeate stream may be directly fed to the recovery column as describedabove.

In certain embodiments of the process of the third aspect, the mixturefeed comprises benzene, toluene, C8 aromatic hydrocarbons, non-aromatichydrocarbon co-boilers of benzene, non-aromatic hydrocarbon co-boilersof toluene, and non-aromatic hydrocarbon co-boilers of C8 aromatichydrocarbons, at a total concentration thereof ≥60 wt % (e.g., ≥65, ≥70,≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weight ofthe mixture feed.

In certain embodiments of the process of the third aspect, the mixturefeed comprises benzene, toluene, non-aromatic hydrocarbon co-boilers ofbenzene, and non-aromatic hydrocarbon co-boilers of toluene, at a totalconcentration thereof ≥60 wt % (e.g., ≥65, ≥70, ≥75, ≥80, ≥85, ≥90, ≥95,≥98, ≥99, wt %), based on the total weight of the mixture feed. SuchC6-C7 hydrocarbon mixture feed can be advantageously derived from, e.g.,distillation of a C6+ hydrocarbon stream derived from a hydrocarbonreformer comprising, in addition to C6-C7 hydrocarbons, C8, C9, andoptionally C9+ hydrocarbons.

In certain embodiments of the process of the third aspect, the mixturefeed comprises benzene and non-aromatic hydrocarbon co-boilers ofbenzene at a total concentration thereof ≥60 wt % (e.g., ≥65, ≥70, ≥75,≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weight of themixture feed.

In certain embodiments of the process of the third aspect, the mixturefeed comprises benzene at a concentration thereof 25 wt % (e.g., ≥25,≥30, ≥35, ≥40, ≥45, ≥50, ≥55, ≥65, ≥70, ≥75, ≥80, ≥85, ≥90, ≥95, ≥98,≥99, wt %), based on the total weight of the mixture feed.

In certain embodiments of the process of the third aspect, the mixturefeed comprises toluene and non-aromatic hydrocarbon co-boilers oftoluene at a total concentration thereof ≥25 wt % (e.g., ≥25, ≥30, ≥35,≥40, ≥45, ≥50, ≥55, ≥65, ≥70, ≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %),based on the total weight of the mixture feed.

In certain embodiments of the process of the third aspect, the mixturefeed comprises toluene at a concentration thereof ≥60 wt % (e.g., ≤65,≥70, ≥75, ≥80, ≥85, ≥90, ≥95, ≥98, ≥99, wt %), based on the total weightof the mixture feed.

In certain embodiments of the process of the second aspect, the processfurther (C-9) providing an isomerization feed stream consistingessentially of C8 aromatic hydrocarbons; (C-10) contacting theisomerization feed stream with an isomerization catalyst in anisomerization zone under isomerization condition to produce anisomerization product mixture; (C-11) separating the isomerizationproduct mixture to obtain a C7−hydrocarbons-rich stream, and a C8+hydrocarbon-rich stream; and (C-12) providing at least a portion of theC7− hydrocarbons-rich stream as the at least a portion of the mixturefeed. In certain specific embodiments, the C7− hydrocarbons-rich streamis substantially free of C8 hydrocarbons. In certain other specificembodiments, the C− hydrocarbon-rich stream comprises C8 hydrocarbons ata concentration from c(C8)1 to c(C8)2 wt %, based on the total weight ofthe C7− hydrocarbon-rich stream, where c(C8)1 and c(C8)2 can be,independently, e.g., 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20. Preferably c(C8)2 ≤10. Preferably c(C8)2 ≤5.

The isomerization conditions can include a temperature and a pressuresuch that a majority of the C8 aromatic hydrocarbons in theisomerization zone are in vapor phase (“vapor-phase isomerization” or“VPI”). Alternatively, the isomerization conditions can include atemperature and a pressure such that a majority of the C8 aromatichydrocarbons in the isomerization zone are in liquid phase(“liquid-phase isomerization” or “LPI”). LPI requires a lowertemperature than VPI, and can be carried out without co-feeding amolecular hydrogen stream into the isomerization zone. As such LPI maybe preferred in certain embodiments over VPI, especially where theisomerization feed stream comprises ethylbenzene at a low concentration.The VPI may be favored where the isomerization feed comprisesethylbenzene at a high concentration, e.g., 10 wt %, based on the totalweight of the isomerization feed stream, because VPI can be moreeffective than LPI in converting ethylbenzene. Description of exemplaryVPI processes and catalysts can be found in, e.g., U.S. PatentApplication Publication Nos. US20110319688A1; US20120108867A1;US20120108868A1; US20140023563A1; US20150051430A1; and US20170081259A1;the relevant contents of all of which are incorporated herein byreference. Description of exemplary LPI processes and catalysts can befound in, e.g., U.S. Patent Application Publication Nos.US20110319688A1; US20120108867A1; US20130274532A1; US20140023563A1; andUS20150051430A1; the relevant contents of all of which are incorporatedherein by reference.

In certain embodiments of the process of the second aspect, the processfurther comprises (C-13) providing a transalkylation feed mixturecomprising C−aromatic hydrocarbons and C9+aromatic hydrocarbons; (C-14)contacting the transalkylation feed mixture with a transalkylationcatalyst in a transalkylation zone under transalkylation conditions toproduce a transalkylation effluent; (C-15) separating thetransalkylation effluent to obtain a benzene-rich stream, and a C8hydrocarbons-rich stream; and (C-16) providing at least a portion of thebenzene-rich stream as the at least a portion of the mixture feed.Description of exemplary transalkylation zone, transalkylation catalyst,and transalkylation conditions can be found in, e.g., U.S. Pat. Nos.7,663,010 and 8,183,424, the relevant contents of both of which areincorporated herein by reference.

In certain embodiments of the process of the second aspect, the processfurther comprises (C-17) providing a toluene disproportionation feedconsisting essentially of toluene; (C-18) contacting the toluenedisproportionation feed with a toluene disproportionation catalyst in adisproportionation zone under disproportionation conditions to produce adisproportionation effluent; (C-19) separating the disproportionationeffluent to obtain a benzene-rich stream, and a C8 hydrocarbons-richstream; and (C-20) providing at least a portion of the benzene-richstream as the at-least a portion of the mixture feed. Description ofexemplary disproportionation zone, disproportionation catalysts, anddisproportionation conditions can be found in, e.g., U.S. Pat. Nos.6,486,373; 7,326,818; and 10,661,258, the relevant contents of all ofwhich are incorporated herein by reference. The disproportionationcatalyst can be shape-selective or non-shape-selective. If ashape-selective catalyst is used, the disproportionation effluent maycomprise p-xylene at a concentration significantly higher than m-xyleneand/or o-xylene, and ethylbenzene at a low concentration, based on thetotal weight of all C8 aromatic hydrocarbons in the disproportionationeffluent, which can be highly advantageous for the purpose ofco-production of a p-xylene product from the process of the first aspectof this disclosure.

In certain embodiments of the process of the second aspect, the processfurther comprises (C-21) providing a C6+ hydrocarbons stream comprisingbenzene, non-aromatic benzene co-boilers, toluene, non-aromatic tolueneco-boilers, C8 aromatic hydrocarbons, non-aromatic co-boilers of C8aromatic hydrocarbons, and C9+ hydrocarbons; (C-22) separating the C6+hydrocarbons stream to obtain a C7− hydrocarbons stream rich in benzeneand toluene, a C7-C8 hydrocarbons stream rich in C8 hydrocarbons, and aC9+ hydrocarbons stream rich in C9+ hydrocarbons; (C-23) feeding atleast a portion of the C7− hydrocarbon stream into the membraneseparator as at least a portion of the mixture feed. Such C6+hydrocarbons stream can be derived from, e.g., an effluent from ahydrocarbons reformer in a petrochemical plant. In specific embodiments,the process may further comprise (C-24) feeding at least a portion ofthe C− hydrocarbon stream into the extraction sub-system column.

In certain embodiments of the process of the second aspect, the processfurther comprises obtaining at least one non-aromatic hydrocarbonproduct stream from the overheads stream. In certain specificembodiments, in step (C-21), at least a portion of the non-aromatichydrocarbon product stream is used as a mogas blending stock.

Detailed Description of the Processes/Systems Illustrated in FIGS. 1 to5

FIG. 1 schematically illustrates the cross-sectional structure andoperation of a membrane separator useful in embodiments of the processesof this disclosure comprising a vessel 101. Vessel 101 comprises aninner conduit and an outer jacket affixed to and surrounding the outersurface of the inner conduit. Vessel 101 comprises a first volume 103, asecond volume 105, and a membrane 107 between volumes 103 and 105.Volume 103 is defined by the inner surface of a wall 115 of the innerconduit. Wall 115 comprises a perforated segment 109 through which fluidcan freely pass. The membrane 107 is shown installed on the outersurface of wall 115 covering the perforated segment 109 in FIG. 1 ,although alternatively or additionally, it may be installed on the innersurface of wall 115. The second volume 105 is defined by the outersurface of wall 115, the outer surface of membrane 107, and the innersurface of the wall 111 of the outer jacket. During operation of themembrane separator, an admixture stream 117 at a first pressurecomprising a first component and a second component having a lowerpolarity than the first component is supplied into the first volume 103through the inlet end of the inner conduit. The admixture stream thenflows along the inner conduit, partly through the perforated segment 109and then contacts the membrane 107. Due to a pressure drop from thefirst volume 103 to the second volume 105, a portion of the firstcomponent and optionally a portion of the second component pass throughthe membrane 107 to enter the second volume 105. Without intending to bebound by a particular theory, it is believed that because the firstcomponent has higher polarity than the second component, passage of thefirst component through the membrane 107 is favored over the secondcomponent, resulting in the formation of a fluid in the second volume105 rich in the first component and depleted in the second componentrelative to admixture stream 117. A portion of the fluid in the secondvolume 105 exits an outlet 113 as a permeate stream 121. The retentatestream 119 exiting from the first volume 103, shown in FIG. 1 at theoutlet end of the inner conduit, is depleted in the first component andrich in the second component relative to the admixture stream 117.

In processes according to the first aspect of this disclosure, theadmixture stream 117 can comprise, e.g., a polar solvent as the firstcomponent, and a hydrocarbon having a lower polarity than the polarsolvent as the second component. Non-limiting examples of the polarsolvent can include, e.g., tetraethylene glycol, triethylene glycol,diethylene glycol, ethylene glycol, methoxy triglycol ether,diglycolamine, dipropylene glycol, N-formyl morpholine, N-methylpyrrolidone, 2,3,4,5-tetrahydrothiophene-1,1-dioxide (“sulfolane”),3-methylsulfolane and dimethyl sulfoxide, tetramethylenesulfone,mixtures thereof, and/or in admixtures with water thereof. Non-limitingexamples of the hydrocarbon can include, aromatic hydrocarbons withvarious boiling points, non-aromatic hydrocarbons with various boilingpoints, and mixtures thereof. In a particularly advantageous embodiment,the hydrocarbon comprises heavy hydrocarbons that may contaminate arecycle lean-solvent stream. In these aspects, the polar solventpreferentially passes through the membrane 107 to become enriched in thesecond volume and the permeate stream and depleted in the retentatestream, and the hydrocarbon(s) preferentially retains and becomesenriched in the first volume and in the retentate stream, and depletedin the second volume and in the permeate stream, relative to theadmixture stream.

In specific embodiments of the first aspect, the admixture stream cancomprise the polar solvent at a concentration of c(ps) wt %, based onthe total weight of the admixture stream, where c(ps) can be in a rangefrom c(ps)1 to c(ps)2, and c(ps)1 and c(ps)2 can be, independently,e.g., 75, 78, 80, 82, 84, 85, 86, 88, 90, 92, 94, 95, 96, 98, 99, 99.9,and even 99.99, as long as c(ps)1<c(ps)2. Preferably c(ps)1=80, andc(ps)2=99. Preferably c(ps)1=85, and c(ps)2=98. Preferably c(ps)1=90,and c(ps)2=97. Additionally, the admixture stream can comprise heavycomponents at a concentration of c(hcom) wt %, based on the total weightof the admixture stream, where c(hcom) can be in a range from c(hcom)1to c(hcom)2, and c(hcom)1 and c(hcom)2 can be, independently, e.g.,0.01, 0.02, 0.04, 0.05, 0.06, 0.08, 0.1, 0.2, 0.4, 0.5, 0.6, 0.8, 1, 2,4, 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, as long as c(hcom)1<c(hcom)2.Preferably c(hcom)=0.1, and c(hcom)=18. Preferably c(hcom)=0.5, andc(hcom)=16. Preferably c(hcom)=1, and c(hcom)=15. Preferably c(hcom)=3,and c(hcom)=14. Preferably c(hcom)=5, and c(hcom)=12.

In processes according to the second aspect of this disclosure, theadmixture stream 117 can comprise an aromatic hydrocarbon as the firstcomponent, and a non-aromatic hydrocarbon as the second component.Preferably the admixture stream is essentially free of a polar solventin the admixture stream in those embodiments. Non-limiting examples ofsuch aromatic hydrocarbon can include, e.g., benzene, toluene, xylenes,ethylbenzene, C9 aromatic hydrocarbons, and mixtures of two or morethereof. Non-limiting examples of such non-aromatic hydrocarbons includenon-aromatic co-boilers of the aromatic hydrocarbon. Without intendingto be bound by a particular theory, it is believed that because anaromatic hydrocarbon tends to exhibit a higher polarity than anon-aromatic hydrocarbon in general, and a non-aromatic hydrocarbonco-boiler thereof in particular, the aromatic hydrocarbon therefore hasa higher affinity than the non-aromatic hydrocarbon in general, and thenon-aromatic hydrocarbon co-boiler thereof in particular, to themembrane in the membrane separator, and as a result passes through themembrane at a higher speed than the non-aromatic hydrocarbon in general,and the non-aromatic hydrocarbon co-boiler thereof in particular. As aresult, the fluid in the second volume and the permeate stream becomesenriched in aromatic hydrocarbon and depleted in the non-aromatichydrocarbon, and the fluid in the retentate stream becomes enriched inthe non-aromatic hydrocarbon and depleted in the aromatic hydrocarbon.

FIG. 2

FIG. 2 schematically illustrates an exemplary extraction process/system201 for separating aromatic hydrocarbons from a mixture feed comprisingaromatic hydrocarbons and non-aromatic hydrocarbons using a membraneseparator 253 to clean an admixture stream comprising a hydrocarbon-leansolvent, according to an embodiment of the first aspect of thisdisclosure. As shown in this figure, a first lean polar solvent stream247 comprising primarily a solvent (e.g., sulfolane) and contaminants(e.g., heavy components) is fed into a membrane separator 253 to producea permeate stream 253 rich in the solvent and depleted in thecontaminants, and a retentate stream 255 rich in the contaminants anddepleted in the solvent. The membrane separator 253 may preferably havea structure and be operated in a manner illustrated in FIG. 1 anddescribed in detail above. The permeate stream 257 can then fed into aliquid-liquid extraction column 209 separately (not shown) or optionallyafter combination with one or more other lean-solvent streams (e.g.,streams 249 (a second lean-solvent stream) and 261, as shown) to form ajoint stream (stream 251, as shown). The retentate stream 255 can thenbe fed into a separator 259, from which a stream 263 rich in thecontaminants (e.g., heavy components) and depleted in the solvent, and alean-solvent stream 261 (a third lean-solvent stream) rich in thesolvent and depleted in the contaminants are produced. It has been foundthat, where stream 255 comprises a significant concentration of heavycomponents achieved by using the membrane separator 253, e.g., aconcentration of 5 wt %, based on the total weight of stream 255, phaseseparation can occur in separator 259 to form a heavy components-richphase and a solvent-rich phase, conveniently effecting the separationand production of streams 261 and 263 from separator 259. Stream 263 canbe conducted away, or optionally after further separation and processingto produce additional products. Stream 261, a thus purified lean-solventstream, can then be fed into the liquid-liquid extraction column 209,either separately (now shown) or optionally after combination with oneor more other lean-solvent streams (e.g., streams 249 and 257, as shown)to form a join stream (stream 251, as shown). Additionally oralternatively, stream 261, or a portion thereof, may be fed into anextraction distillation column (not shown) to facilitate extractiondistillation of a mixture feed comprising aromatic hydrocarbons andnon-aromatic hydrocarbons. Additionally or alternatively (now shown),stream 261, or a portion thereof, may be fed into a stripping column(e.g., columns 267 and 231, as shown) to facilitate separation. Invarious embodiments of the processes of the first aspect of thisdisclosure, by using a membrane separator, a lean-solvent streamcontaining contaminants (e.g., a recycle lean-solvent stream after asubstantial operation period), or a portion thereof, can be convenientlypurified under mild conditions with low energy consumption, lowmaintenance, low capital investment, and low operation costs.

As shown in FIG. 2 , the first lean-solvent stream 247 and the secondlean-solvent stream 249 can be derived from a common lean-solvent stream245. Stream 247 can be turned off in certain embodiments, especiallywhere the common stream 245 has a high solvent purity indicated by arelatively low total concentration of the contaminants (e.g., a lowtotal concentration of the heavy components therein, c(hcom-cs) wt %,based on the total weight of stream 245, e.g., where c(hcom-cs) <3, orc(hcom-cs) <1, or c(hcom-cs) <0.5). In those cases purification of aportion of stream 245 by using the membrane separator 253 is notnecessary. Thus, in a preferred embodiment, one can monitor theconcentration of the contaminants in the common lean-solvent stream 245,e.g., c(hcom-cs), and turn on the first lean-solvent stream 247 onlywhen it reaches a threshold level, e.g., where c(hcom-cs) ≥0.5, orc(hcom-cs) ≥1, or c(hcom-cs) ≥3, or even c(hcom-cs) ≥5. Preferablyc(hcom-cs) ≤20, or c(hcom-cs) ≤18, or c(hcom-cs) ≤16, or c(hcom-cs) ≤15,or c(hcom-cs) ≤12. As indicated above, at a high concentration of thecontaminants in stream 245 and thus stream 247, (e.g., a highc(hcom-cs)), an even higher concentration of the contaminants inretentate stream 255 is achieved, which can conveniently effect adesirable phase separation in separator 259. While it is possible toshut off the second lean-solvent stream 249 completely so that theentirety of stream 245 becomes stream 247 and treated in the membraneseparator 253, preferably stream 249 constitutes only a small portion ofstream 245. Thus, in preferred embodiments, where in a given timeperiod, the first lean-solvent stream 247 comprises the solvent at atotal weight of W1, the second lean-solvent stream 249 comprises thesolvent at a total weight of W2, streams 247 and 249 are regulated suchthat 0.5% ≤W1/(W1+W2)*100% ≤10%, preferably 0.5% ≤W1/(W1+W2)*100% ≤8%,preferably 0.5% ≤W1/(W1+W2)*100% ≤5%, more preferably 1%≤W1/(W1+W2)*100% ≤5%, still more preferably 1% ≤W1/(W1+W2)*100% ≤3%.

The overall process/system of FIG. 2 is now described as follows.

A mixture feed stream 203 comprising aromatic hydrocarbons andnon-aromatic hydrocarbons, produced from, e.g., a naphtha reformatestream, a xylenes isomerization effluent stream, a transalkylationeffluent stream, a toluene disproportionation effluent stream, or thelike, or a mixture thereof, and recycle hydrocarbon streams 205 and 206derived from a common stream 207, also comprising aromatic hydrocarbonsand non-aromatic hydrocarbons, are fed into a liquid-liquid distillationcolumn 209 (alternatively, an extraction distillation column, not shown)at various locations on the column. A recycle lean-solvent stream 251 isfed into column 209 at a location above streams 203, 205, and 206.Inside column 209, the polar solvent admixes with the hydrocarbons anddescends to the bottom to produce a rich-solvent stream 219 rich inaromatic hydrocarbons and depleted in non-aromatic hydrocarbons relativeto stream 203. From the top, a stream 211 rich in non-aromatichydrocarbons and depleted in aromatic hydrocarbons relative to stream203 is produced.

Stream 219, upon being heated at heat exchanger 243 by a recyclelean-solvent stream 239, becomes stream 265 and can be fed into astripping column 267 optionally along with a steam stream 221 to producean overhead stream 269 comprising steam and rich in non-aromatichydrocarbons relative to stream 265 and a bottoms rich-solvent stream271 rich in aromatic hydrocarbons. Stream 271 can be split into stream272 for recycling to column 267 and stream 273 for feeding intodistillation column 275.

Stream 211 from the top of column 209 can be supplied to a water washcolumn 213 along with a water-rich stream 281, from which a non-aromatichydrocarbon stream 215 and an aqueous stream 217 are produced. Stream215, optionally after additional treatment such as drying and/orseparation, can be used or made into various non-aromatic hydrocarbonproducts, e.g., mogas blending stocks. Stream 217, comprisinghydrocarbons and water, can be then fed into a steam stripping column231, along with a steam stream 295, optionally after combination withother aqueous streams such as stream 227 produced from a phase separator225 to form a joint stream 229.

From the top of column 231, a hydrocarbon/steam mixture stream 233 and abottoms stream 235 comprising solvent and water are produced. Stream233, optionally after combination with stream 269 described above, canbe condensed and then phase-separated in phase separator 225 to producea hydrocarbon stream 207 and an aqueous stream 227. Stream 207 can thenbe recycled to column 209 as described above. Stream 227 can be combinedwith stream 217 to form stream 229 as described above. Stream 235 fromthe bottom of column 231 can then be fed into a steam generator 237,where it is heated by hot lean-solvent stream 289 to produce a steamstream 293 and a solvent-rich stream 296. Steam stream 293 can be splitinto streams 294 and 295. Stream 295 can be fed into steam strippingcolumn 231 as described above.

Steam stream 294, along with an aromatic hydrocarbons-rich solventstream 273, solvent-rich stream 296, and an optional lean-solvent stream292 produced from a solvent regenerator 291, can then be fed intodistillation column 275, to produce an aromatic hydrocarbon/steammixture stream 277 from the top and a hot, lean-solvent stream 286 fromthe bottom. Stream 277, upon condensing (not shown) is then separated inphase separator 279 to obtain an aqueous stream 281 and an aromatichydrocarbon stream 283. Stream 281 can be fed to water wash column 213as described above. Stream 283 can be split into streams 284 recycled tocolumn 275 and stream 285, which, upon optional additional processingsuch as drying and distillation, can be used as or made into variousaromatic hydrocarbon products, e.g., benzene, toluene, benzene/toluenemixture, and the like.

The hot lean-solvent stream 286 exiting the bottom of column 275 can besplit into stream 287 for recycling to column 275 upon further heatingvia a heat exchanger, stream 290 for regeneration in the solventregenerator 291 to produce a regenerated solvent stream 292, and stream289 fed into steam generator 237 to heat stream 235 to produce steamstream 293 as described above. The cooled lean-solvent stream 239exiting steam generator 237 can be further cooled down by therich-solvent stream 219 produced at the bottom of column 209 at a heatexchanger 243 to form the common lean-solvent stream 245 as describedabove. Solvent regenerator 291 can be, e.g., a steam stripping column, avacuum regenerator column, a sorbent bed column containing a bed of asorbent such as ion exchange resins, inorganic sorbent materials, andcombinations thereof. As a result of the use of membrane separator 253to de-contaminate at least a portion of recycle lean-solvent stream 245as described above, the solvent regenerator 291, if already existing,can be de-commissioned or operated only intermittently, or not installedor installed with a reduced capacity in a grass-root plant, resulting insavings in equipment investment and/or operation costs.

FIG. 3

FIG. 3 schematically illustrates an exemplary extraction process/system301 for separating aromatic hydrocarbons from a mixture feed comprisingaromatic hydrocarbons and non-aromatic hydrocarbons using a membraneseparator 305, according to embodiments of the second aspect of thisdisclosure. As shown in this figure, a mixture feed stream 303comprising aromatic hydrocarbons and non-aromatic hydrocarbons, e.g., astream derived from an effluent exiting a C8 aromatic hydrocarbonisomerization unit (not shown), is fed into a membrane separator 305comprising a membrane between a first and a second volumes, preferablyhaving a structure and operated in a manner illustrated in FIG. 1 asdescribed above, to produce a permeate stream 307 rich in aromatichydrocarbons and depleted in non-aromatic hydrocarbons relative tostream 303, and a retentate stream 309 rich in non-aromatic hydrocarbonsand depleted in aromatic hydrocarbons relative to stream 303. Stream 309may still comprise aromatic hydrocarbons at various quantity, especiallywhere stream 303 comprises aromatic hydrocarbons at a highconcentration, e.g., where stream 303 consists essentially of aromatichydrocarbons with a total concentration of aromatic hydrocarbons of,e.g., ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt %, or ≥98 wt %, based on thetotal weight of stream 303. Stream 309 can then be optionally combinedwith another mixture feed source stream 311 derived from, e.g., anaphtha reformate stream, to form a joint stream 313, which can then befed into an extraction separation sub-system 315 to produce anon-aromatic hydrocarbons stream 317 (e.g., a high-purity non-aromatichydrocarbon stream) and an extracted aromatic hydrocarbons stream 319(e.g., a high-purity aromatic hydrocarbon stream, preferably a streamessentially free of non-aromatic hydrocarbons). The extractionseparation sub-system 315 can comprise, e.g., an extraction column(e.g., an liquid-liquid extraction column, or an extraction distillationcolumn, preferably a liquid-liquid extraction column), one or morestripping columns, an aromatic hydrocarbon-solvent separationdistillation column, a lean solvent recycle loop for recycling at leasta portion of the lean-solvent stream into the extraction column), andother ancillary equipment, such as those illustrated in FIG. 2 anddescribed above. The two aromatic hydrocarbon streams, the permeatestream 307 from the membrane separator and stream 319 from theextraction separation sub-system 315, can then be combined to form ajoint stream 321, which is then fed into an aromatics hydrocarbonseparation column 323, from which multiple aromatic product streams suchas stream 325 (e.g., a high-purity benzene stream), stream 327 (e.g., abenzene/toluene mixture stream), stream 329 (a high-purity toluenestream), and stream 331 (a C8+ hydrocarbons stream) can be produced.Alternatively or additionally, a portion or the entirety of theretentate stream 309 and/or the non-aromatic hydrocarbons stream 317 canbe conducted away and/or made into various products, such as motor gasblending stocks.

A contemplated comparative process/system (not shown) is identical tothose of FIG. 3 except that the membrane separator 305 is not installed,and as a result, to remove the non-aromatic hydrocarbons contained instream 303, the entirety of stream 303 is combined with stream 311 toform stream 313, which is then fed into the extraction sub-system 315.Compared to the comparative process/system, the process/system of FIG. 3can result in significant savings over time due to much less energyconsumption by separating a portion of the aromatic hydrocarbons fromstream 303 using the membrane separator and only feeding thenon-aromatic hydrocarbons-rich portion 309 thereof into the extractionsub-system 315. The installation of the membrane separator 305 canpotentially reduce the capacity required of the extraction sub-system315 in a grass-root plant resulting in savings in capital expenditure,or enable it to process a larger quantity from stream 311 if themembrane separator 305 is retrofitted into an existing aromatichydrocarbons production plant resulting in increased productivity. Wherestream 303 comprises a high concentration of aromatic hydrocarbons, theprocess/system of FIG. 3 can be particularly advantageous, because thearomatic hydrocarbons-rich permeate stream 307 can constitute a majorportion of stream 303, and only a small portion of stream 303 (i.e.,stream 309) is fed into the extraction sub-system 315. In contrast, inthe comparative process/system, where stream 303 comprises aromatichydrocarbons at a high concentration and is nonetheless fed into theextraction sub-system 315 in its entirety, a much larger quantity ofaromatic hydrocarbons passes through the extraction sub-system,requiring a higher-capacity extraction sub-system and resulting insignificant energy loss.

In a preferred embodiment of the process/system 301, stream 303 cancomprise benzene, toluene, non-aromatic hydrocarbon co-boilers ofbenzene, and non-aromatic hydrocarbon co-boilers of toluene at a totalconcentration thereof ≥60 wt %, ≥65 wt %, ≥70 wt %, ≥75 wt %, ≥80 wt %,≥85 wt %, ≥90 wt %, ≥95 wt %, based on the total weight of stream 303.In specific embodiments thereof, stream 303 can comprise benzene andtoluene at a total concentration thereof ≥60 wt %, ≥65 wt %, ≥70 wt %,≥75 wt %, ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt %, based on the totalweight of stream 303. In specific embodiments thereof, stream 303 cancomprise benzene at a total concentration thereof ≥60 wt %, ≥65 wt %,≥70 wt %, ≥75 wt %, ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt %, based on thetotal weight of stream 303.

In a preferred embodiment (not shown) of the process/system 301, atleast a portion of stream 303 can be produced by: (B-11) providing anisomerization feed stream consisting essentially of C8 aromatichydrocarbons; (B-12) contacting the isomerization feed stream with anisomerization catalyst in an isomerization zone under isomerizationconditions to produce an isomerization product mixture; (B-13)separating the isomerization product mixture to obtain a C7−hydrocarbons-rich stream, and a C8+ hydrocarbon-rich stream; and (B-14)providing at least a portion of the C7− hydrocarbons-rich stream as atleast a portion of stream 303. Exemplary C8 aromatic hydrocarbonisomerization processes and systems are described in, e.g., U.S. PatentApplication Publication Nos. US20110319688A1; US20120108867A1;US20120108868A1; US20140023563A1; US20150051430A1; and US20170081259A1;the relevant contents of all of which are incorporated herein byreference in their entirety. C8 aromatic hydrocarbon isomerizationprocesses and systems (aka “isomerization units”) can be used to convertone or more of ethylbenzene, m-xylene, and o-xylene into more valuableproducts such as benzene and p-xylene.

In another preferred embodiment (not shown) of the process/system 301,at least a portion of stream 303 can be produced by: (B-15) providing atransalkylation feed mixture comprising C7− aromatic hydrocarbons andC9+ aromatic hydrocarbons; (B-16) contacting the transalkylation feedmixture with a transalkylation catalyst in a transalkylation zone undertransalkylation conditions to produce a transalkylation effluent; (B-17)separating the transalkylation effluent to obtain a benzene-rich stream,and a C8 hydrocarbons-rich stream; and (B-18) providing at least aportion of the benzene-rich stream as at least a portion of stream 303.Exemplary transalkylation processes and systems are described in, e.g.,U.S. Pat. Nos. 7,663,010 and 8,183,424, the relevant contents of both ofwhich are incorporated herein by reference in their entirety.Transalkylation processes and systems (aka “transalkylation units”) canbe used to convert C9+ aromatic hydrocarbons and toluene into morevaluable products such as benzene and xylenes, particularly p-xylene ifcombined with an isomerization process/system.

In another preferred embodiment (not shown) of the process/system 301,at least a portion of stream 303 can be produced by: (B-19) providing atoluene disproportionation feed consisting essentially of toluene;(B-20) contacting the toluene disproportionation feed with a toluenedisproportionation catalyst in a disproportionation zone underdisproportionation conditions to produce a disproportionation effluent;(B-21) separating the disproportionation effluent to obtain abenzene-rich stream, and a C8 hydrocarbons-rich stream; and (B-22)providing at least a portion of the benzene-rich stream as at least aportion of stream 303. Exemplary toluene disproportionation processesand systems are described in, e.g., U.S. Pat. Nos. 7,326,818 and10,661,258, the relevant contents of both of which are incorporatedherein by reference in their entirety. Toluene disproportionationprocesses and systems (aka “transalkylation units”) can be used toconvert toluene into more valuable products such as benzene and xylenes,particularly p-xylene.

FIG. 4

FIG. 4 schematically illustrates an exemplary extraction process/system401 for separating aromatic hydrocarbons from a mixture feed comprisingaromatic hydrocarbons and non-aromatic hydrocarbons using a membraneseparator 413, according to embodiments of the second aspect of thisdisclosure. As shown in this figure, a C6+ hydrocarbons stream 403comprising benzene, non-aromatic benzene co-boilers, toluene,non-aromatic toluene co-boilers, C8 aromatic hydrocarbons, non-aromaticco-boilers of C8 aromatic hydrocarbons, and C9+ hydrocarbons is fed intoa separation column 405 to obtain a C7− hydrocarbons stream 407, a C7−C8 hydrocarbons stream 411, and a C9+ hydrocarbon stream 409. Stream 403can be derived from a reformate stream produced from a reformer in apetrochemical plant. Stream 407, rich in benzene, benzene co-boilers,toluene, and toluene co-boilers, can be combined with other similarstreams, such as stream 417 described below, and then fed into anextraction separation sub-system 421. Stream 409 can be fed into atransalkylation unit (now shown) along with a benzene/toluene stream toproduce additional quantity of xylenes. Stream 411, comprising toluene,co-boilers of toluene, C8 aromatic hydrocarbons and co-boilers thereof,can be then fed into a membrane separator 413 comprising a membranebetween a first and a second volumes, preferably having a structure andoperated in a manner illustrated in FIG. 1 as described above, toproduce a permeate stream 415 rich in toluene and C8 aromatichydrocarbons and depleted in non-aromatic hydrocarbons relative tostream 411, and a retentate stream 417 rich in non-aromatic hydrocarbonsand depleted in aromatic hydrocarbons relative to stream 411. Stream 417may still comprise aromatic hydrocarbons at various quantity, especiallywhere stream 411 comprises aromatic hydrocarbons at a highconcentration, e.g., where stream 411 consists essentially of aromatichydrocarbons with a total concentration of aromatic hydrocarbons of,e.g., ≥50 wt %, ≥60 wt %, ≥70 wt %, ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt%, or ≥98 wt %, based on the total weight of stream 411. Stream 417 canthen be combined with another mixture feed source stream, such as stream407, to form a joint stream 419, which can then be fed into anextraction separation sub-system 421 to produce a non-aromatichydrocarbons stream 423 (e.g., a high-purity non-aromatic hydrocarbonstream) and an extracted aromatic hydrocarbons stream 425 (e.g., ahigh-purity aromatic hydrocarbon stream, preferably a stream essentiallyfree of non-aromatic hydrocarbons). The extraction separation sub-system421 can comprise, e.g., an extraction column (e.g., an liquid-liquidextraction column, or an extraction distillation column, preferably aliquid-liquid extraction column), one or more stripping columns, anaromatic hydrocarbon-solvent separation distillation column, a leansolvent recycle loop for recycling at least a portion of thelean-solvent stream into the extraction column, and other ancillaryequipment, such as those illustrated in FIG. 2 and described above. Thetwo aromatic hydrocarbon streams, the permeate stream 415 from themembrane separator 413 and stream 425 from the extraction separationsub-system 421, can then be combined to form a joint stream 427 and fedinto an aromatics hydrocarbon separation column 429, from which multiplearomatic product streams such as stream 431 (e.g., a high-purity benzenestream), stream 433 (e.g., a benzene/toluene mixture stream), stream 435(a high-purity toluene stream), and stream 437 (a C8 aromatichydrocarbons stream) can be produced. These various aromatic hydrocarbonstreams can be used as high-quality feeds for various downstreamprocesses, e.g., transalkylation, xylene isomerization, toluenedisproportionation, benzene/toluene methylation for making xylenes, andthe like. Alternatively or additionally, a portion or the entirety ofthe retentate stream 417 and/or the non-aromatic hydrocarbons stream 423can be conducted away and/or made into various products, such as motorgas blending stocks.

A contemplated first comparative process/system (not shown) to that ofFIG. 4 is identical to that of FIG. 4 except that the membrane separator413 is not present, and stream 411 is fed into a second extractionseparation sub-system (now shown) to produce another aromatichydrocarbon stream and another non-aromatic hydrocarbon stream. Theother aromatic hydrocarbon stream can then be fed into column 429together with stream 425. Compared to the process/system of FIG. 4 ,this first comparative process/system requires much more equipment,costs significantly higher, and consumes more energy.

A contemplated second comparative process/system (not shown) to those ofFIG. 4 is identical to those of FIG. 4 except that the membraneseparator 413 is not present, and stream 411 is fed directly into adownstream process such as isomerization, disproportionation, and thelike. Stream 411 contains significant amount of non-aromatics andtherefore is inferior to high-quality streams 433, 435, and 437 whichcontain less or close to no non-aromatic hydrocarbons, for downstreamprocesses. As such, this second comparative process/system can causeundesirable side reactions and produce undesirable by-products andresult in less efficiency, lower process stability, shorter processruntime, and the like, to the downstream processes, compared to theprocess/system of FIG. 4 .

FIG. 5

FIG. 5 schematically illustrates an exemplary extraction process/system501 for separating aromatic hydrocarbons from a mixture feed comprisingaromatic hydrocarbons and non-aromatic hydrocarbons using a membraneseparator 511, according to an embodiment of the third aspect of thisdisclosure. As shown in this figure, a mixture feed stream 503comprising aromatic hydrocarbons and non-aromatic hydrocarbons, e.g., astream derived a reformate effluent stream (not shown), is fed into anextraction column 505 (e.g., a liquid-liquid extraction column or anextraction distillation column, preferably a liquid-liquid extractioncolumn), along with a lean-solvent stream 525 and a recyclehydrocarbon-containing stream 515 described below. From column 505, anoverhead stream 509 rich in non-aromatic hydrocarbons and depleted inaromatic hydrocarbons relative to stream 503, and a bottoms rich-solventstream 507 rich in aromatic hydrocarbons and depleted in non-aromatichydrocarbons are produced. To achieve a high degree of extraction ofaromatic hydrocarbons in column 505, the process may be configured suchthat stream 507 nonetheless comprises substantial quantity ofnon-aromatic hydrocarbons and stream 509 can be substantially free ofaromatic hydrocarbons. A split stream 509 from stream 507 (as shown) orthe entirety of stream 507 can be then fed into a membrane separator 513comprising a membrane between a first and a second volumes, preferablyhaving a structure and operated in a manner in FIG. 1 as describedabove, to produce a permeate stream 517 rich in aromatic hydrocarbonsand depleted in non-aromatic hydrocarbons relative to stream 509, and aretentate stream 515 rich in non-aromatic hydrocarbons and depleted inaromatic hydrocarbons relative to stream 509. Stream 515 may nonethelesscomprise aromatic hydrocarbons at a substantial quantity, in addition tothe solvent and non-aromatic hydrocarbons. Thus stream 515 is preferablyrecycled back to column 505, from which aromatic hydrocarbons can beextracted. Stream 517, depleted in non-aromatic hydrocarbons relative tostream 509 and comprising the solvent, can then be fed into an aromatichydrocarbons/solvent separation sub-system 521, which can comprise,e.g., a distillation column and optional equipment such as a strippingcolumn (not shown). From the separation sub-system 521, a high-purityaromatic hydrocarbons stream 523 and a lean-solvent stream 525 (a secondlean-solvent stream) are produced. The second lean-solvent stream 525,or a portion thereof, can then be recycled to the extraction column 505.A portion or the entirety of the non-aromatic hydrocarbons stream 509can be conducted away and/or made into various products, such as motorgas blending stocks. Stream 523 can be further separated to make one ormore aromatic hydrocarbon streams (e.g., a high-purity benzene stream, atoluene-benzene mixture stream, a toluene stream, and the like).

A contemplated comparative process/system (not shown) is identical tothose of FIG. 5 except that the membrane separator 513 is not installedand the entirety of stream 507 is fed into aromatic hydrocarbons/solventseparation sub-system 521. Compared to the comparative process/system,the process/system of FIG. 5 can result in significant savings over timedue to much less energy consumption by separating a portion of thearomatic hydrocarbons from stream 507 using the membrane separator andonly feeding the aromatic hydrocarbons-rich portion 517 thereof into theseparation sub-system 521. The installation of the membrane separator305 can potentially reduce the capacity and number of equipment requiredof the separation sub-system 521 in a grass-root plant resulting insavings in capital expenditure, or enable it to process a largerquantity from stream 519 if the membrane separator 513 is retrofittedinto an existing aromatic hydrocarbons production plant resulting inincreased productivity. Where stream 507 comprises a relatively highconcentration of non-aromatic hydrocarbons, the process/system of FIG. 5can be particularly advantageous, because the non-aromatichydrocarbons-rich retentate stream 515 can constitute a significantportion of stream 507, and only a significantly smaller portion ofstream 507 (i.e., stream 517) is fed into the extraction sub-system 521.In contrast, in the comparative process/system, where stream 507comprises non-aromatic hydrocarbons at a significant concentration andis nonetheless fed into the separation sub-system 521 in its entirety, amuch larger quantity of non-aromatic hydrocarbons needs to be separatedin the separation sub-system 521, requiring a higher-capacity extractionsub-system 521 with more equipment (e.g., stripping column) andresulting in significant energy loss.

In a preferred embodiment of the process/system 501, stream 503 cancomprise benzene, toluene, non-aromatic hydrocarbon co-boilers ofbenzene, and non-aromatic hydrocarbon co-boilers of toluene at a totalconcentration thereof ≥60 wt %, ≥65 wt %, ≥70 wt %, ≥75 wt %, ≥80 wt %,≥85 wt %, ≥90 wt %, ≥95 wt %, based on the total weight of stream 303.In specific embodiments thereof, stream 503 can comprise benzene andtoluene at a total concentration thereof ≥25 wt %, ≥30 wt %, ≥35 wt %,≥40 wt %, ≥45 wt %, ≥50 wt %, ≥55 wt %, ≥60 wt %, ≥65 wt %, ≥70 wt %,≥75 wt %, ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt %, based on the totalweight of stream 303. In specific embodiments thereof, stream 303 cancomprise benzene at a total concentration thereof ≥25 wt %, ≥30 wt %,≥35 wt %, ≥40 wt %, ≥45 wt %, ≥50 wt %, ≥55 wt %, ≥60 wt %, ≥65 wt %,≥70 wt %, ≥75 wt %, ≥80 wt %, ≥85 wt %, ≥90 wt %, ≥95 wt %, based on thetotal weight of stream 303.

In a preferred embodiment (now shown) of the process/system 501, atleast a portion of stream 503 can be produced by: (C-9) providing anisomerization feed stream consisting essentially of C8 aromatichydrocarbons; (C-10) contacting the isomerization feed stream with anisomerization catalyst under isomerization condition to produce anisomerization product mixture; (C-11) separating the isomerizationproduct mixture to obtain a C7− hydrocarbons-rich stream, and a C8+hydrocarbon-rich stream; and (C-12) providing at least a portion of theC7− hydrocarbons-rich stream as the at least a portion of stream 503.

In another preferred embodiment (not shown) of the process/system 501,at least a portion of stream 503 can be produced by: (C-13) providing atransalkylation feed mixture comprising C7− aromatic hydrocarbons andC9+ aromatic hydrocarbons; (C-14) contacting the transalkylation feedmixture with a transalkylation catalyst under transalkylation conditionsto produce a transalkylation effluent; (C-15) separating thetransalkylation effluent to obtain a benzene-rich stream, and a C8hydrocarbons-rich stream; and (C-16) providing at least a portion of thebenzene-rich stream as the at least a portion of stream 503.

In another preferred embodiment (not shown) of the process/system 501,at least a portion of stream 503 can be produced by: (C-17) providing atoluene disproportionation feed consisting essentially of toluene;(C-18) contacting the toluene disproportionation feed with a toluenedisproportionation catalyst under disproportionation conditions toproduce a disproportionation effluent; (C-19) separating thedisproportionation effluent to obtain a benzene-rich stream, and a C8hydrocarbons-rich stream; and (C-20) providing at least a portion of thebenzene-rich stream as the at least a portion of stream 503.

In yet another preferred embodiment (not shown) of the process/system501, at least a portion of stream 503 can be produced by: (C-21)providing a C6+ hydrocarbons stream comprising benzene, non-aromaticbenzene co-boilers, toluene, non-aromatic toluene co-boilers, C8aromatic hydrocarbons, non-aromatic co-boilers of C8 aromatichydrocarbons, and C9+ hydrocarbons; (C-22) separating the C6+hydrocarbons stream to obtain a C7− hydrocarbons stream rich in benzeneand toluene, a C7− C8 hydrocarbons stream rich in C8 hydrocarbons, and aC9+ hydrocarbons stream rich in C9+ hydrocarbons; and (C-23) feeding atleast a portion of the C7− hydrocarbon stream into the membraneseparator as the at least a portion of the mixture feed at least aportion of stream 503.

This disclosure can include one or more of the following non-limitingaspects and/or embodiments.

Listing of Embodiments

A1. A process for extracting aromatic hydrocarbons from a mixture feedcomprising aromatic hydrocarbons and non-aromatic hydrocarbons, theprocess comprising:

-   -   (A-1) feeding the mixture feed into an extraction column;    -   (A-2) providing a first lean-solvent stream comprising a polar        solvent at a concentration of c(ps) wt %, and heavy components        at a total concentration of c(hcom) wt %, based on the total        weight of the lean-solvent stream, where 75 ≤c(ps) ≤99.99;    -   (A-3) feeding the first lean-solvent stream into a membrane        separator, wherein: the membrane separator comprises a vessel        having a first volume, a second volume, and a membrane between        the first volume and the second volume; the first volume is        separated from the second volume by the membrane; the membrane        is more permeable to the polar solvent than to the heavy        components; and the first lean-solvent stream is fed into the        first volume;    -   (A-4) obtaining a retentate stream exiting the first volume of        the membrane separator, wherein the retentate steam is rich in        the heavy components relative to the first lean-solvent stream;    -   (A-5) obtaining a permeate stream exiting the second volume of        the membrane separator, wherein the permeate stream is depleted        in the heavy components relative to the first lean-solvent        stream; and    -   (A-6) feeding at least a portion of the permeate stream into the        extraction column.

A2. The process of A1, further comprising:

-   -   (A-7) phase separating at least a portion of the retentate        stream to obtain a heavy components stream and a solvent stream        saturated with heavy components; and    -   (A-8) feeding at least a portion of the solvent stream saturated        with heavy components to the extraction column.

A3. The process of A2, wherein the solvent stream saturated with heavycomponents comprises the heavy components at a total concentration in arange from 3 to 15 wt %, based on the total weight of the solvent streamsaturated with the heavy components.

A4. The process of any of A1 to A3, wherein:

-   -   the extraction column is an extraction distillation column.

A5. The process of any of A1 to A4, wherein:

-   -   the extraction column is a liquid-liquid extraction column.

A6. The process of any of A1 to A5, wherein:

-   -   the polar solvent is selected from tetraethylene glycol,        triethylene glycol, diethylene glycol, ethylene glycol, methoxy        triglycol ether, diglycolamine, dipropylene glycol, N-formyl        morpholine, N-methyl pyrrolidone,        2,3,4,5-tetrahydrothiophene-1,1-dioxide (“sulfolane”),        3-methylsulfolane and dimethyl sulfoxide, tetramethylenesulfone,        mixtures thereof, and/or admixtures with water thereof.

A7. The process of any of A1 to A6, wherein:

-   -   the membrane comprises a polyimide membrane, or a membrane        comprising an ionic liquid.

A8. The process of any of A1 to A7, wherein:

-   -   the first lean-solvent stream has a temperature in a range from        25 to 80° C. when fed into the membrane separator, and a        positive pressure gradient of deltaP kPa exists from the first        volume to the second volume of the membrane separator, and        deltaP ranges from 345 to 10,342.

A9. The process of any of A1 to A8, wherein 0.01 ≤c(hcom) ≤20.

A10. The process of A9, wherein 1≤c(hcom) ≤15.

A11. The process of any of A1 to A10, further comprising:

-   -   (A-9) feeding a second lean-solvent stream comprising the polar        solvent into the extraction column.

A12. The process of All, wherein in a given time period, the firstlean-solvent stream comprises the polar solvent at a total weight of W1,the second lean-solvent stream comprises the polar solvent at a totalweight of W2, and 0.5% ≤W1/(Wl+W2)*100% ≤10%.

A13. The process of A12, wherein 0.5% ≤W1/(W1+W2)*100% ≤8%, preferably0.5% W1/(W1+W2)*100% ≤5%, more preferably 1% ≤W1/(W1+W2)*100% ≤5%, stillmore preferably 1% ≤W1/(W1+W2)*100% ≤3%.

A14. The process of A9 or A10, wherein the first lean-solvent stream andthe second lean-solvent stream are derived from a common lean-solventstream.

A15. The process of A14, wherein the common lean-solvent stream comprisethe heavy components at a total concentration of c(hcom-cs) wt %, basedon the total weight of the common lean-solvent stream, and the processfurther comprises:

-   -   (A-10) monitoring c(hcom-cs); and    -   (A-11) implementing step (A-3) to (A-8) only if c(hcom-cs) ≤1.

A16. The process of any of A1 to A15, further comprising:

-   -   (A-12) obtaining a bottoms stream from the extraction column,        wherein the bottoms stream is rich in aromatic hydrocarbons and        the polar solvent relative to the mixture feed;    -   (A-13) separating at least a portion of the bottoms stream in a        stripping column to obtain an aromatic hydrocarbons-rich stream        comprising steam and depleted in the polar solvent relative to        the bottoms stream, and a third lean-solvent stream depleted in        aromatic hydrocarbons relative to the bottoms stream; and    -   (A-14) deriving at least one of the first lean-solvent stream,        the second lean-solvent stream, and the common lean-solvent        stream from the third lean-solvent stream.

A17. The process of A16, further comprising:

-   -   (A-15) deriving a fourth lean-solvent stream from the third        lean-solvent stream;    -   (A-16) regenerating the fourth lean-solvent stream in a steam        stripping regeneration column and/or a vacuum regeneration        column to obtain a regenerated lean-solvent stream comprising        steam and a bottoms heavy stream; and    -   (A-17) feeding the regenerated lean-solvent stream into one or        more of: the stripping column, the extraction column, and the        membrane separator as at least a portion of the first        lean-solvent stream.

A18. The process of A17, further comprising:

-   -   (A-18) condensing at least a portion of the aromatic        hydrocarbons-rich stream to obtain a mixture comprising an        aqueous liquid phase and an oil liquid phase;    -   (A-19) separating the aqueous liquid phase to obtain a water        stream;    -   (A-20) heating the water stream to obtain a steam stream; and    -   (A-21) feeding the steam stream to the steam stripping        regeneration column and/or the vacuum regeneration column.

A19. The process of A18, wherein in step (A-21), the steam stream is atleast partly heated by a portion of the third lean-solvent stream.

A20. A process for extracting aromatic hydrocarbons from a mixture feedcomprising aromatic hydrocarbons and non-aromatic hydrocarbons, theprocess comprising:

-   -   (A-1) feeding the mixture feed into an extraction column;    -   (A-2) providing a first lean-solvent stream comprising a polar        solvent at a concentration of c(ps) wt %, and heavy components        at a total concentration of c(hcom) wt %, based on the total        weight of the lean-solvent stream;    -   (A-3) feeding the first lean-solvent stream into a membrane        separator, wherein: the membrane separator comprises a vessel        having a first volume, a second volume, and a membrane between        the first volume and the second volume; the first volume is        separated from the second volume by the membrane; the membrane        is more permeable to the polar solvent than to the heavy        components; and the first lean-solvent stream is fed into the        first volume;    -   (A-4) obtaining a retentate stream exiting the first volume of        the membrane separator, wherein the retentate steam is rich in        the heavy components relative to the first lean-solvent stream;    -   (A-5) obtaining a permeate stream exiting the second volume of        the membrane separator, wherein the permeate stream is depleted        in the heavy components relative to the first lean-solvent        stream;    -   (A-6) feeding at least a portion of the permeate stream into the        extraction column;    -   (A-9) feeding a second lean-solvent stream comprising the polar        solvent into the extraction column,    -   wherein in a given time period, the first lean-solvent stream        comprises the polar solvent at a total weight of W1, the second        lean-solvent stream comprises the polar solvent at a total        weight of W2, and 0.5% W1/(W1+W2)*100% ≤10%.

B1. A process for separating a mixture feed comprising aromatichydrocarbons and non-aromatic hydrocarbons, the process comprising:

-   -   (B-1) feeding the mixture feed into a membrane separator,        wherein: the membrane separator comprises a vessel having a        first volume, a second volume, and a membrane between the first        volume and the second volume; the first volume is separated from        the second volume by the membrane; the membrane is more        permeable to the aromatic hydrocarbons than to the non-aromatic        hydrocarbons; and the mixture feed is fed into the first volume;    -   (B-2) obtaining a retentate stream exiting the first volume of        the membrane separator, wherein the retentate steam is depleted        in the aromatic hydrocarbons and rich in the non-aromatic        hydrocarbons relative to the mixture feed; and    -   (B-3) obtaining a permeate stream exiting the second volume of        the membrane separator, wherein the permeate stream is rich in        the aromatic hydrocarbons and depleted in the non-aromatic        hydrocarbons relative to the mixture feed.

B2. The process of B1, further comprising:

-   -   (B-4) feeding at least a portion of the retentate stream and an        extraction solvent stream into an extraction sub-system;    -   (B-5) obtaining from the extraction sub-system a non-aromatic        hydrocarbons stream, an extracted aromatic hydrocarbons stream,        and a lean-solvent stream; and    -   (B-6) recycling at least a portion of the lean-solvent stream        into the extraction sub-system as at least a portion of the        extraction solvent stream.

B3. The process of B1 or B2, further comprising:

-   -   (B-7) feeding at least a portion of the permeate stream and at        least a portion of the extracted aromatic hydrocarbon stream        into an aromatic hydrocarbons distillation column; and    -   (B-8) obtaining from the aromatic hydrocarbons distillation        column two or more aromatic product streams.

B4. The process of B1 or B2, further comprising:

-   -   (B-9) feeding at least a portion of the permeate stream and/or a        least a portion of the extracted aromatic hydrocarbon stream        into a reactor; and    -   (B-10) producing a converted product mixture from the reactor.

B5. The process of any of B1 to B4, wherein the mixture feed comprisesbenzene, toluene, non-aromatic hydrocarbon co-boilers of benzene, andnon-aromatic hydrocarbon co-boilers of toluene at a total concentrationthereof ≥60 wt %, based on the total weight of the mixture feed.

B6. The process of any of B1 to B5, further comprising:

-   -   (B-11) providing an isomerization feed stream consisting        essentially of C8 aromatic hydrocarbons;    -   (B-12) contacting the isomerization feed stream with an        isomerization catalyst in an isomerization zone under        isomerization condition to produce an isomerization product        mixture;    -   (B-13) separating the isomerization product mixture to obtain a        C7− hydrocarbons-rich stream, and a C8+ hydrocarbon-rich stream;        and    -   (B-14) providing at least a portion of the C7− hydrocarbons-rich        stream as the at least a portion of the mixture feed.

B6a. The process of B6, wherein the C7− hydrocarbons-rich stream issubstantially free of C8 hydrocarbons.

B6 b. The process of B6, wherein the C7− hydrocarbon-rich streamcomprises C8 hydrocarbons at a concentration from c(C8)1 to c(C8)2 wt %,based on the total weight of the C7− hydrocarbon-rich stream, wherec(C8)1 and c(C8)2 can be, independently, e.g., 0.5, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. Preferably c(C8)2 ≤10.Preferably c(C8)2 ≤5.

B7. The process of any of B1 to B6b, further comprising:

-   -   (B-15) providing a transalkylation feed mixture comprising C7−        aromatic hydrocarbons and C9+ aromatic hydrocarbons;    -   (B-16) contacting the transalkylation feed mixture with a        transalkylation catalyst in a transalkylation zone under        transalkylation conditions to produce a transalkylation        effluent;    -   (B-17) separating the transalkylation effluent to obtain a        benzene-rich stream, and a C8 hydrocarbons-rich stream; and    -   (B-18) providing at least a portion of the benzene-rich stream        as the at least a portion of the mixture feed.

B8. The process of any of B1 to B7, further comprising:

-   -   (B-19) providing a toluene disproportionation feed consisting        essentially of toluene;    -   (B-20) contacting the toluene disproportionation feed with a        toluene disproportionation catalyst in a disproportionation zone        under disproportionation conditions to produce a        disproportionation effluent;    -   (B-21) separating the disproportionation effluent to obtain a        benzene-rich stream, and a C8 hydrocarbons-rich stream; and    -   (B-22) providing at least a portion of the benzene-rich stream        as the at-least a portion of the mixture feed.

B9. The process of any of B5 to B8, wherein the mixture feed comprises≥75 wt % of benzene and toluene combined, based on the total weight ofthe mixture feed.

B10. The process of B9, wherein the mixture feed comprising ≥90 wt % ofbenzene, based on the total weight of the mixture feed.

B11. The process of any of B1 to B3, wherein the mixture feed comprisesbenzene, toluene, C8 aromatic hydrocarbons, non-aromatic hydrocarbonco-boilers of benzene, non-aromatic hydrocarbon co-boilers of toluene,and non-aromatic hydrocarbon co-boilers of C8 aromatic hydrocarbons at atotal concentration thereof ≥60 wt %, based on the total weight of themixture feed.

B12. The process of any of B1 to B11, further comprising:

-   -   (B-23) providing a C6+hydrocarbons stream comprising benzene,        non-aromatic benzene co-boilers, toluene, non-aromatic toluene        co-boilers, C8 aromatic hydrocarbons, non-aromatic co-boilers of        C8 aromatic hydrocarbons, and C9+ hydrocarbons;    -   (B-24) separating the C6+ hydrocarbons stream to obtain a C7−        hydrocarbons stream rich in benzene and toluene, a C7− C8        hydrocarbons stream rich in C8 hydrocarbons, and a C9+        hydrocarbons stream rich in C9+ hydrocarbons;    -   (B-25) feeding at least a portion of the C7− hydrocarbon stream        into the membrane separator as at least a portion of the mixture        feed.

B13. The process of B12, further comprising:

-   -   (B-26) feeding at least a portion of the C7− hydrocarbon stream        into the extraction sub-system column.

B14. The process of any of B1 to B13, further comprising:

-   -   (B-23) conducting away at least a portion of the retentate        stream and/or at least a portion of the non-aromatic hydrocarbon        stream.

B15. The process of B14, wherein in step (B-23), the at least a portionof the retentate stream and/or the at least a portion of thenon-aromatic hydrocarbon stream is used as a mogas blending stock.

B16. The process of any of B1 to B15, further comprising:

-   -   (B-24) feeding at least a portion of the retentate stream into        the extraction sub-system.

B17. The process of any of B1 to B16, wherein the polar solvent isselected from tetraethylene glycol, triethylene glycol, diethyleneglycol, ethylene glycol, methoxy triglycol ether, diglycolamine,dipropylene glycol, N-formyl morpholine, N-methyl pyrrolidone,2,3,4,5-tetrahydrothiophene-1,1-dioxide (“sulfolane”), 3-methylsulfolaneand dimethyl sulfoxide, tetramethylenesulfone, mixtures thereof, and/oradmixtures with water thereof.

B18. The process of any of B1 to B17, wherein the a mixture feed is inliquid phase.

C-1. A process for separating a mixture feed comprising aromatichydrocarbons and non-aromatic hydrocarbons, the process comprising:

-   -   (C-1) feeding the mixture feed and a first lean-solvent stream        comprising a polar solvent into an extraction column;    -   (C-2) obtaining an overhead stream and a bottoms stream from the        extraction column, wherein the overhead stream is rich in        non-aromatic hydrocarbons relative to the mixture feed, the        bottoms stream is rich in aromatic hydrocarbons and the polar        solvent relative to the mixture feed;    -   (C-3) feeding at least a portion of the bottoms stream into a        membrane separator, wherein: the membrane separator comprises a        vessel having a first volume, a second volume, and a membrane        between the first volume and the second volume; the first volume        is separated from the second volume by the membrane; the        membrane is more permeable to the aromatic hydrocarbons than to        the non-aromatic hydrocarbons; and the at least a portion of the        bottoms stream is fed into the first volume;    -   (C-4) obtaining a retentate stream exiting the first volume of        the membrane separator, wherein the retentate steam is depleted        in the aromatic hydrocarbons and rich in the non-aromatic        hydrocarbons relative to the bottoms stream;    -   (C-5) obtaining a permeate stream exiting the second volume of        the membrane separator, wherein the permeate stream is rich in        the aromatic hydrocarbons and depleted in the non-aromatic        hydrocarbons relative to the bottoms stream; and    -   (C-6) feeding at least a portion of the retentate stream to the        extraction column.

C2. The process of C1, further comprising:

-   -   (C-7) obtaining at least an aromatic hydrocarbons-rich stream        and a second lean-solvent stream from the permeate stream,        wherein the second lean-solvent stream is rich in the polar        solvent relative to the permeate steam; and    -   (C-8) recycling at least a portion of the second lean-solvent        stream to the extraction column as at least a portion of the        first lean-solvent stream.

C3. The process of C1 or C2, wherein the extraction column is anextraction distillation column.

C3a. The process of C3, wherein step (C-7) comprises feeding at least aportion of the permeate stream to a recovery distillation column, fromwhich the aromatic hydrocarbons-rich stream and the second lean-solventstream are obtained.

C4. The process of C1 or C2, wherein the extraction column is aliquid-liquid extraction column.

C4b. The process of C4, wherein step (C-7) comprises:

-   -   (C-7a) feeding at least a portion of the permeate stream to a        stripping column, from which an overhead stream and a bottoms        stream are produced, wherein the bottoms stream is rich in        aromatic hydrocarbons and comprise the polar solvent;    -   (C-7b) feeding the bottoms stream from the stripping column to a        recovery distillation column, from which the aromatic        hydrocarbons-rich stream and the second lean-solvent stream are        obtained.

C5. The process of any of C1 to C4b, wherein:

-   -   the polar solvent is selected from tetraethylene glycol,        triethylene glycol, diethylene glycol, ethylene glycol, methoxy        triglycol ether, diglycolamine, dipropylene glycol, N-formyl        morpholine, N-methyl pyrrolidone,        2,3,4,5-tetrahydrothiophene-1,1-dioxide (“sulfolane”),        3-methylsulfolane and dimethyl sulfoxide, tetramethylenesulfone,        mixtures thereof, and/or admixtures with water thereof.

C6. The process of any of C1 to C5, wherein:

-   -   the membrane comprises a polyimide membrane, or a membrane        comprising an ionic liquid.

C7. The process of any of C1 to C6, wherein the mixture feed comprises≥25 wt % of benzene and toluene combined, based on the total weight ofthe mixture feed.

C8. The process of any of C1 to C7, wherein the mixture feed comprisesbenzene, toluene, C8 aromatic hydrocarbons, non-aromatic hydrocarbonco-boilers of benzene, non-aromatic hydrocarbon co-boilers of toluene,and non-aromatic hydrocarbon co-boilers of the C8 aromatic hydrocarbonsat a total concentration ≥60 wt %, based on the total weight of themixture feed.

C9. The process of any of C1 to C8, further comprising:

-   -   (C-9) providing an isomerization feed stream consisting        essentially of C8 aromatic hydrocarbons;    -   (C-10) contacting the isomerization feed stream with an        isomerization catalyst in an isomerization zone under        isomerization condition to produce an isomerization product        mixture;    -   (C-11) separating the isomerization product mixture to obtain a        C7− hydrocarbons-rich stream, and a C8+ hydrocarbon-rich stream;        and    -   (C-12) providing at least a portion of the C7− hydrocarbons-rich        stream as the at least a portion of the mixture feed.

C9a. The process of C9, wherein the C7− hydrocarbons-rich stream issubstantially free of C8 hydrocarbons.

C9b. The process of C9, wherein the C7− hydrocarbon-rich streamcomprises C8 hydrocarbons at a concentration from c(C8)1 to c(C8)2 wt %,based on the total weight of the C7− hydrocarbon-rich stream, wherec(C8)1 and c(C8)2 can be, independently, e.g., 0.5, 1, 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20. Preferably c(C8)2 ≤10.Preferably c(C8)2 ≤5.

C10. The process of any of C1 to C9b, further comprising:

-   -   (C-13) providing a transalkylation feed mixture comprising C7−        aromatic hydrocarbons and C9+ aromatic hydrocarbons;    -   (C-14) contacting the transalkylation feed mixture with a        transalkylation catalyst in a transalkylation zone under        transalkylation conditions to produce a transalkylation        effluent;    -   (C-15) separating the transalkylation effluent to obtain a        benzene-rich stream, and a C8 hydrocarbons-rich stream; and    -   (C-16) providing at least a portion of the benzene-rich stream        as the at least a portion of the mixture feed.

C11. The process of any of C1 to C10, further comprising:

-   -   (C-17) providing a toluene disproportionation feed consisting        essentially of toluene;    -   (C-18) contacting the toluene disproportionation feed with a        toluene disproportionation catalyst in a disproportionation zone        under disproportionation conditions to produce a        disproportionation effluent;    -   (C-19) separating the disproportionation effluent to obtain a        benzene-rich stream, and a C8 hydrocarbons-rich stream; and    -   (C-20) providing at least a portion of the benzene-rich stream        as the at-least a portion of the mixture feed.

C12. The process of any of C8 to C11, wherein the mixture feed comprises≥75 wt % of benzene and toluene combined, based on the total weight ofthe mixture feed.

C13. The process of C12, wherein the mixture feed comprising ≥90 wt % ofbenzene, based on the total weight of the mixture feed.

C14. The process of any of C1 to C7, wherein the mixture feed comprisesbenzene, toluene, C8 aromatic hydrocarbons, non-aromatic hydrocarbonco-boilers of benzene, non-aromatic hydrocarbon co-boilers of toluene,and non-aromatic hydrocarbon co-boilers of C8 aromatic hydrocarbons at atotal concentration thereof ≥60 wt %, based on the total weight of themixture feed.

C15. The process of C14, further comprising:

-   -   (C-21) providing a C6+ hydrocarbons stream comprising benzene,        non-aromatic benzene co-boilers, toluene, non-aromatic toluene        co-boilers, C8 aromatic hydrocarbons, non-aromatic co-boilers of        C8 aromatic hydrocarbons, and C9+ hydrocarbons;    -   (C-22) separating the C6+ hydrocarbons stream to obtain a C7−        hydrocarbons stream rich in benzene and toluene, a C7− C8        hydrocarbons stream rich in C8 hydrocarbons, and a C9+        hydrocarbons stream rich in C9+ hydrocarbons;    -   (C-23) feeding at least a portion of the C7− hydrocarbon stream        into the membrane separator as at least a portion of the mixture        feed.

C16. The process of C15, further comprising:

-   -   (C-24) feeding at least a portion of the C7− hydrocarbon stream        into the extraction sub-system column.

C17. The process of any of C1 to C16, further comprising:

-   -   (C-21) obtaining at least one non-aromatic hydrocarbon product        stream from the overheads stream.

C18. The process of C17, wherein at least a portion of the non-aromatichydrocarbon product stream is used as a mogas blending stock.

What is claimed is:
 1. A process for extracting aromatic hydrocarbonsfrom a mixture feed comprising aromatic hydrocarbons and non-aromatichydrocarbons, the process comprising: (A-1) feeding the mixture feedinto an extraction column; (A-2) providing a first lean-solvent streamcomprising a polar solvent at a concentration of c(ps) wt %, and heavycomponents at a total concentration of c(hcom) wt %; based on the totalweight of the lean-solvent stream, where 75 ≤c(ps) ≤99.99; (A-3) feedingthe first lean-solvent stream into a membrane separator, wherein: themembrane separator comprises a vessel having a first volume, a secondvolume, and a membrane between the first volume and the second volume;the first volume is separated from the second volume by the membrane;the membrane is more permeable to the polar solvent than to the heavycomponents; and the first lean-solvent stream is fed into the firstvolume; (A-4) obtaining a retentate stream exiting the first volume ofthe membrane separator, wherein the retentate steam is rich in the heavycomponents relative to the first lean-solvent stream; (A-5) obtaining apermeate stream exiting the second volume of the membrane separator,wherein the permeate stream is depleted in the heavy components relativeto the first lean-solvent stream; and (A-6) feeding at least a portionof the permeate stream into the extraction column.
 2. The process ofclaim 1, further comprising: (A-7) phase separating at least a portionof the retentate stream to obtain a heavy components stream and asolvent stream saturated with heavy components; and (A-8) feeding atleast a portion of the solvent stream saturated with heavy components tothe extraction column.
 3. The process of claim 2, wherein the solventstream saturated with heavy components comprises the heavy components ata total concentration in a range from 3 to 15 wt %, based on the totalweight of the solvent stream saturated with the heavy components.
 4. Theprocess of claim 1, wherein: the extraction column is an extractiondistillation column.
 5. The process of claim 1,. wherein: the extractioncolumn is a liquid-liquid extraction column.
 6. The process of claim 1,wherein: the polar solvent is selected from tetraethylene glycol,triethylene glycol, diethylene glycol, ethylene glycol, methoxytriglycol ether, diglycolamine, dipropylene glycol, N-formyl morpholine,N-methyl pyrrolidone, 2,3,4,5-tetrahydrothiophene-1,1-dioxide(“sulfolane”), 3-methylsulfolane and dimethyl sulfoxide,tetramethylenesulfone, mixtures thereof, and/or admixtures with waterthereof.
 7. The process of claim 1, wherein: the membrane comprises apolyimide membrane, and/or a membrane comprising an ionic liquid.
 8. Theprocess of claim 1, wherein: the first lean-solvent stream has atemperature in a range from 25 to 80° C. when fed into the membraneseparator, and a positive pressure gradient of deltaP kPa exists fromthe first volume to the second volume of the membrane separator, anddelta ranges from 345 to 10,342 kilopascal.
 9. The process of claim 1,wherein 0.01 ≤c(hcom) ≤20.
 10. The process of claim 9, wherein 1≤c(hcom) ≤15.
 11. The process of claim 1, further comprising: (A-9)feeding a second lean-solvent stream comprising the polar solvent intothe extraction column.
 12. The process of claim 11, wherein in a giventime period, the first lean-solvent stream comprises the polar solventat a total weight of the second lean-solvent stream comprises the polarsolvent at a total weight of W2, and 0.5% ≤W1/(W1+W2)*100% ≤10%.
 13. Theprocess of claim 12, wherein 0.5% ≤W1/(W1+W2)*100% ≤8%.
 14. The processof claim 11, wherein the first lean-solvent stream and the secondlean-solvent stream are derived from a common lean-solvent stream. 15.The process of claim 14, wherein the common lean-solvent stream comprisethe heavy components at a total concentration of c(hcom-cs) wt %, basedon the total weight of the common lean-solvent stream, and the processfurther comprises: (A-10) monitoring c(hcom-cs); and (A-11) implementingstep (A-3) to (A-8) only if c(hcom-cs) ≥1.
 16. The process of claim 1.further comprising: (A-12) obtaining a bottoms stream from theextraction column, wherein the bottoms stream is rich in aromatichydrocarbons and the polar solvent relative to the mixture feed; (A-13)separating at least a portion of the bottoms stream in a strippingcolumn to obtain an aromatic hydrocarbons-rich stream comprising steamand depleted in the polar solvent relative to the bottoms stream, and athird lean-solvent stream depleted in aromatic hydrocarbons relative tothe bottoms stream; and (A-14) deriving at least one of the firstlean-solvent stream, the second lean-solvent stream, and the commonlean-solvent stream from the third lean-solvent stream.
 17. The processof claim 16, further comprising: (A-15) deriving a fourth lean-solventstream from the third lean-solvent stream; (A-16) regenerating thefourth lean-solvent stream in a steam stripping regeneration columnand/or a vacuum regeneration column to obtain a regenerated lean-solventstream comprising steam and a bottoms heavy stream; and (A-17) feedingthe regenerated lean-solvent stream into one or more of the strippingcolumn, the extraction column, and the membrane separator as at least aportion of the first lean-solvent stream.
 18. The process of claim 17,further comprising: (A-18) condensing at least a portion of the aromatichydrocarbons-rich stream to obtain a mixture comprising an aqueousliquid phase and an oil liquid phase; (A-19) separating the aqueousliquid phase to obtain a water stream; (A-20) heating the water streamto obtain a steam stream; and (A-21) feeding the steam stream to thesteam stripping regeneration column.
 19. The process of claim 18,wherein in step (A-21), the steam stream is at least partly heated by aportion of the third lean-solvent stream.
 20. A process for extractingaromatic hydrocarbons from a mixture feed comprising aromatichydrocarbons and non-aromatic hydrocarbons, the process comprising:(A-1) feeding the mixture feed into an extraction column; (A-2)providing a first lean-solvent stream comprising a polar solvent at aconcentration of c(ps) wt %, and heavy components at a totalconcentration of c(hcom) wt %, based on the total weight of thelean-solvent stream; (A-3) feeding the first lean-solvent stream into amembrane separator, wherein: the membrane separator comprises a vesselhaving a first volume, a second volume, and a membrane between the firstvolume and the second volume; the first volume is separated from thesecond volume by the membrane; the membrane is more permeable to thepolar solvent than to the heavy components; and the first lean-solventstream is fed into the first volume; (A-4) obtaining a retentate streamexiting the first volume of the membrane separator, wherein theretentate steam is rich in the heavy components relative to the firstlean-solvent stream; (A-5) obtaining a permeate stream exiting thesecond volume of the membrane separator, wherein the permeate stream isdepleted in the heavy components relative to the first lean-solventstream; (A-6) feeding at least a portion of the permeate stream into theextraction column; (A-9) feeding a second lean-solvent stream comprisingthe polar solvent into the extraction column, wherein in a given timeperiod, the first lean-solvent stream comprises the polar solvent at atotal weight of W1, the second lean-solvent stream comprises the polarsolvent at a total weight of W2, and 0.5% ≤W1/(W1+W2)*100% ≤10%.